Hi there, I realise this thread is a few months old- but being a Clothie Mum I wished to impart some NIGHT NAPPY ADVICE!
I too found after a time that my tots bots weren't keeping Jacob dry at night- but i found an alternative to dispoables as overnight nappies.
I use an apparently miracle combination of- Nappies by Minki pocket nappy- and a Cotton Bottom's prefold as the 'stuffing' in the middle. the minki nappies are FABULOUS- they are completely fleece lined- meaning nice and dry against baby's bum, (although it does bobble over time it's still softer than soggy terry next to their skin) and you just stuff the nappy pocket to your required level of absorbancy.
Even with Jacob (now 2 and half) we use them overnight with the 'Large' cotton bottom prefold inside and he's dry in the morning.
I really can't praise them enough- they are extra bulky as nappies, but under PJ's that's not the end of the world!
You can see the designs and available sizes on my fave nappy website- kittykins.co.uk - I have been using the slinki minkis on both boys- a Medium size fit Benji from 3 months old (with less stuffing inside) and kept him dry through the night - and with Jacob we used the Large size from 5 months up til now- adjusting the absorbancy required as he got bigger.
The regular minki nappies are cut VERY generously- (the Large reg Minki would easily fit Jacob until he was four or five if he was prone to the odd accident by then still) so I would recommend Slinki Minkis unless you have a chunky monkey tot 
I hope that helped someone! I have even converted usually disposable mums to using a Minki at night for soggy toddlers who also get the 'exploding nappy' problem usually.