Fleece nappies would be very hot to wear if babies didn't wee in them. But as soon as they are wet there is automatically exavporation / moisture permeability happening , and this is cooling.So as long as your baby is weeing then fleece nappies are fine even in hot weather.
Pop'n'gros make a fab night-time nappy as you can put in both boosters - bothe the bamboo one and the big fluffly microfibre one. Plus the nappy itself has some built in microfibre for some absorbency, unlike most AIOs where the inserts have to go into a pocket or be poppered in. I would think it would be almost impossible to outwee a pop'n'gro for that reason. Plus you can now buy the bamboo boosters separately if you just wanted to layer slimmer bamboo boosters.
If anyone wants to try a pop'n'gro or order separate bammboo boosters I will give 10% off to anyone from Mumsnet. (I'm going on holiday tomorrow for nearly a week, so get your request to me tonight or after next Monday!)