Armitage Shanks 8½`` Bottom Entry Fill Valve Quiet Part 4 equilibrium 8½ fixed height bottom inlet fill valve. For toilet cistern or storage tank. http://www.comparestoreprices.co.uk/january-2017-9/armitage-shanks-8½-bottom-entry-fill-valve.asp
Here's one with the door at the thin end at 4ft x 8ft (122 x 244cm). A door opening outwards helps things along, as do shallow sinks. Another tip is to nestle the sink and toilet cistern into niches in the wall which means them stick out less into the room. The minimum width you can get away with is about 4ft (122cm).