Every WordPress site eventually outgrows the plugin directory. The theme assumes a workflow that isn’t yours, the form tool can’t quite do what your sales process needs, and the reports you want live in software that doesn’t talk to your site yet.
We build custom WordPress development around your exact requirements: plugins, theme functionality, WooCommerce extensions, and integrations, tested properly on staging before anything touches your live site.
The WordPress plugin directory has over 60,000 entries, and between them they cover most of what a website needs to do. That is the strength of the platform, and the limit of it. When your requirements get specific, a pricing tool that mirrors your quote engine, a client portal fed by your accounting software, a checkout flow that matches how you actually fulfil orders, the ready-made option either doesn’t exist or bends your process around someone else’s assumptions.
We write WordPress code that fits your business instead. Custom plugins, custom post types, admin screens, and integrations built on the platform’s own APIs, so your site stays updateable and any competent developer can pick the work up afterwards.
What sets this apart:
This is not a page of shortcodes held together with hope. It is engineered software, running on your infrastructure, maintained to the same standard we hold our own sites to.
Every build follows the same four-stage workflow we use across all our development work.
Step 1: Discovery and specification. We document exactly what the site needs to do, what data it handles, and how it fits into your wider systems. You approve the written specification before a single line of code is written.
Step 2: Architecture and prototyping. We decide how the feature fits WordPress, which post types, tables, and APIs are involved, and where it touches existing plugins. For anything complex, you get a working prototype to click through before the full build starts.
Step 3: Development and testing. The build happens on a staging copy of your site. We test against your real content and data, cover the edge cases, and review security on everything that accepts input. You get access to try it, break it, and request changes.
Step 4: Deployment and handover. We migrate the finished work to your live site, set up backups before we touch anything, and hand over the documentation. Afterwards you own the code outright, no licences, no lock-in, no monthly dependency on us.
Honest answer: most sites don’t need as much custom work as they think. We always start by checking whether a proven plugin, a configuration change, or a small fix gets you there first. Custom development is for the moment when your requirement is genuinely specific, and paying for it is cheaper than bending your business around someone else’s software.
Not if it’s built correctly. We write against WordPress’s own APIs and use child themes, so core updates, theme updates, and security patches continue to work around our code rather than through it. That’s exactly why we avoid patching plugin files directly, the shortcut that causes most of the update disasters we get called to fix.
Yes. We audit your current setup first: plugins, theme, database, hosting, and anything already custom. Most of our development work happens on established sites, where the goal is to add capability without disturbing what’s already performing well. We test everything on a staging copy before it touches production.
A focused feature, like a custom calculator or a CRM integration, typically runs two to four weeks. Larger builds with portals or complex WooCommerce logic take longer. We give you a fixed scope, price, and timeline at the specification stage, so there are no surprises on the invoice.
We help businesses make smarter decisions online, with clear advice and practical digital solutions that support long-term growth.
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Paul and his team are very professional, they have given good advice, and built a great site that generates ongoing business
Sum Factors not only delivered us a great website, they also provided advice and support to bring in traffic and orders. At every point, they have been highly professional and responsive, and nothing is too much trouble. Really enjoyed working with Paul and his team and would highly recommend Sum Factors.
It been great working with Sumfactors. I know very little about the tech side of things especially when it comes to Google ads and Website updates. But both Karen and Paul have been amazing. Taking me through everything step by step. The best thing about them is you feel they genuinely care about growing your business. It's as if it is their business too and that makes them an absolute pleasure to work with.
Sumfactor (aka wonderful Paul) always has my best interest at heart, it's so rare to come across an agency who not only knows what they're doing but you can 100% trust. Paul will openly Challenge on my decisions even if it means him making less money at times as long as it's in my best interest he'll say what he has to say and I'm so great full for that. Couldn't recommend them more
What would we (and our website) do without them - timely accurate absolute pleasure to work with - it feels like we have personal coaches for our business at hand whenever we need technical, design or even psychological support in how to tackle a business problem. They are a blessing to our business - couldn't be in safer hands on all accounts!
I would recommend SumFactors to anyone who is looking for more than just a website designer. Paul met with me and straight away understood my business and where I wanted to take it. His knowledge and experience has been invaluable, creating the website and digital strategy which has been part of RBHM's success. Paul is friendly and really easy to work with, always happy to help.
We were introduced to Sum Factors over a year ago when we opened our business and needed a website and they were - and still are fantastic! The website is very professional but - most importantly - the ongoing support is priceless! nothing is too much, things get done very quickly and Paul and Karen are the nicest team you can work with!
We have worked with SumFactors for many years and would highly recommend their knowledge, expertise and personal/efficient service, but above all their proven ability to go the extra mile time after time! A fabulous team who are passionate, dedicated and an absolute pleasure to work with. Kim Barnes - Evans FREC MD THE Agency (Recruitment) Ltd West Yorkshire
A great experience working with Paul and the team. Very supportive and informative. Great value for money and their ability to help us grow the business is a real asset. Will certainly be using again!
Cannot fault anything that the guys at SumFactors carry out. From initial concept, right the way through to publishing and aftercare, they really do take care of everything - making running a small business much easier. Paul & Karen have changed the way I view my website and how it should perform, giving me a personalised service that is simply not available elsewhere at this price point! Thank you for all of your help, Sam S.Thomas Kitchens
I have recently started working with SumFactors on Fletcher Of London and they have been great. Really lovely people to work with, they are quick to respond, and always there to offer support and advice. They have shown me how to manage my own products and shop so now I feel confident to do more things for myself. I would highly recommend SumFactors.
I am so impressed with the service I have received working with the Sumfactors team. Nothing is ever too much trouble, they are incredibly creative and knowledgeable. They are experts in their field but go out of their way to understand our business and our goals and work with us to achieve these. Their prices are extremely competitive. I would recommend Sumfactors to any company or sole trader any time. From the team at Inspire Me Travel
I'm so pleased with my new website, set up relatively recently by Sum Factors. It has attracted a number of new clients very quickly and my website looks very professional and attractive. Paul and Karen are so helpful, friendly and professional and I would highly recommend them
SumFactors are a pleasure to work with and genuine experts in their field. They are helpful, affordable and insightful and I would wholeheartedly recommend them to anyone who is interested in their services - you will not regret it.
