Thanks girls.
Ill have a look for the sheet protectors and find some night time undies.
I know its normal just frustrating.
You could try brolly sheets as well (different brand) but that's what I found easiest. DS1 is doing the I want to wear undies to bed thing but not staying dry as well so I get that. I offer the pajama pants/night pull ups most nights when I help dress him for bed and sometimes he uses them sometimes not. (DH doesn't usually offer as DS wants to be in undies mostly)
I found that I've needed 3-4 brolly sheets sometimes (I was trying for 1-2 but when DS2 moved to a big bed I got a couple extras as spares and needed them when they didn't have a chance to dry)