About us

High-performing websites for organisations who value their digital assets

Castlegate IT is a specialist WordPress design and development agency founded in York in 2011. In the fifteen years since, we have built and maintained websites for global brands, national charities, cultural institutions, and household names. But we have always understood that a website is not an end in itself. It is a business asset, and it needs to work hard for the organisation behind it.

That understanding shapes everything we do. We bring together deep technical expertise, considered design, and strategic thinking to deliver websites that serve a clear purpose: helping our clients achieve their goals online.

Our people are what make the difference. Every senior member of staff is a subject matter expert, and we build project teams with the precise combination of skills each project demands.

Trusted by organisations that rely on their website

The organisations that choose to work with Castlegate IT are not looking for a supplier. They are looking for a partner that understands what is at stake, and has the experience to deliver. Our clients include national charities, academic networks, cultural institutions, manufacturing companies, and public sector organisations. They range considerably in size, but they share three priorities:

They take their digital presence seriously and trust us to keep it secure, stable, and future-proof.

They want a long-term website partner that is genuinely invested in their success.

They run websites where downtime is not an option. For them, it means lost income, missed opportunities, and damaged reputation.

If this sounds like your organisation, we would welcome the opportunity to discuss how we can help.

A collaborative approach to every project

We collaborate closely with our clients from the outset, asking the right questions to understand their priorities and ensure that every decision supports their goals.

Once we have a clear shared vision, we design and build to fit. We are not constrained by off-the-shelf solutions, and our expertise means we can develop custom-coded websites that meet requirements unique to your organisation.

We combine technical precision, creative thinking, and rigorous project management to deliver websites that exceed our clients’ expectations and equip them to grow with confidence.

Our history

Jim Semlyen founded Semlyen IT Consultants in 2005, offering web development services to businesses in and around York. His personal approach and technical attention to detail meant the company grew quickly in both size and reputation. In 2011, it became Castlegate IT Ltd, and Jim was joined by Richard Lane and Andy Reading as company directors.

By 2015, the team had grown to 12, spanning design, development, and project management, and we moved to a new, larger office on Walmgate. We remain proud of our York roots and continue to work with businesses of all sizes across the region. Today, our client base includes national and international organisations that value our dedication, honesty, and high standards. Our approach has remained constant throughout: we care about our clients and bring the same attention to detail to every project we undertake.

Our mission, values and goals

Understanding what drives us matters, both to the people who work here and to the organisations we work with. We have spent many years thinking carefully about the direction of Castlegate IT, and what we stand for.

Our mission, values, and goals are published in full because we believe that transparency builds better partnerships. They also help prospective clients decide whether we are the right fit for them.

Our ethical policy

Working in the digital world does not diminish our responsibility to the physical one. Castlegate IT holds itself to high standards of ethical and environmental behaviour, above and beyond our legal obligations. Our ethical policy sets out exactly what that means in practice.