The floorspace for the 33L, 50L, and 64L are all the same and a little bigger than my adult rack, so if you want to give lots of climbing room I'd go for the 64L. Otherwise the 50L does still have a little room for smaller branches and decorations.
http://www.amazon.co.uk/Really-Usef..._cp_229_3?ie=UTF8&refRID=1P6P4DVB80YXD1469QEP
http://www.amazon.co.uk/Really-Usef...&sr=8-1&keywords=really+useful+boxes+50+litre
I think most of the brands available to you aren't found much in the US, so I don't know how much help I can be. I've used Zoo Med mats, just added foil to the adhesive size instead of sticking it on permanently. They definitely require a thermostat, since they can get over 45ºC, some nearly 50ºC. I have another small mat right now that holds perfect temperature without a thermostat, but I couldn't tell you the brand. I'd just browse your options on amazon and check out the reviews.