air conditioning?

moving for postgraduate study to edinburgh and living in an apartment. do i need AC for september to may? does it generally feel unbearably hot at night? i'm a light sleeper so ideally i'd like to order a portable AC now and set it up.

also, if anyone does have an AC, which one? i'd ideally like a quiet one that works quite well, as i'll be using it for a while, i don't have a budget.

thanks in advance!