A massive bunch of newbie questions.

[Sugarbit]

I'd get a mini UTH, not sure what kind they have in UK but it should only take up 1/2 of the bottom at most. Be sure to get a thermostat too, they get real hot....even the small ones

Yep, the thermostat's on it's way in the post. Would 150 x 280mm (7 Watts) be OK? There's also an even smaller one which is 102 x 127mm (4 watts). Haha I'm not sure what qualifies as mini!