if you are set on a one box aero system, like filthyfletch or any of the diy 30 min aero systems out there, then almost everything will leak (im in NA so i can only offer general res advice). I use a rubbermaid, but it's not one of the roughnecks that inherently don't leak. My res has two layers of plastic sheeting (like painting dripcloth, or thin vapor barrier) over the top, then a layer of reflectix (attic insulation). The rectangles of plastic sheeting and reflectix have holes for the net pots, and the plstic sheets are cut a foot wider the the res lid on all sides. Once the lid is on, the plastic sheeting gets tucked inside the res on all 4 sides, thus making it entirely leak proof with practicaly no work. I found my res temperature went up when i sealed my res, so i now have a computer fan exchanging the air insde the res.
U could also use industrial garbage bags to line the res and then tape the sides up onto the lid of the res. this way you never need to scrub the inside down either, just empty and pop in a new bag. Helps with light tightness too, although i haven't seen that as a problem with my own grow.
If your s;pace is a specific size and you require a specific sized res, it will probably be advantageous to not need one that is also entirely leak proof. You can leak proof any container easily, but i hope someone can suggest a UK alternative to the roughneck for you all the same.
gl
