Does anyone have any websites for tanks in the UK or where to get a custom built one?
As we have a custom built one:
I would suggest asking around some glass companies. That was our solution as here in Chile supplies are very hard to get and even if, super expensive as imported plus high shipping costs even within the country. I just prepared an e-mail with what I wanted, asking how much this might cost.
(Glass companies likely can also make "extras" like sliding front doors...
Because of the language barrier we still face here in Chile, we opted for a simpler solution with an aquarium-like tank and I added the screen top (made it from wood, two robust hinges, and a wide-mesh screen) on my own. Also works very well.)