I definitely recommend using a framework and in my experience Laravel would be the best fit for you. You can easily integrate what you have already built into it by either using Blade (the template system) or the pages you already have. To get started I would put your existing pages in the views folder and then create routes to them. Doing this is fairly straight forward and a good first step where you will see immediate results. From there you can start to extract your code to models and controllers and really start to make use of the framework.

Thanks for your input Nylad. I'm just about to install Laravel now. We'll see how it goes.

Thanks again.