Oh yeah I meant to update this after trying them.
To be honest I haven't found them as good as I hoped, BUT I've only tried them with one of the boosters so far, think I need to try with both, also I think they may need a few more washes to reach full absorbency. The bamboo fabric takes a lot of drying too.
Another thing I saw on the nappy hunt was brolly sheets. They are a mattress protector that goes on top of the top sheet so you only have to change that, they look quite good but not sure if they come in a cot size. Can't remember which sites on the nappy hunt had them, but I see Mothers Instinct does
here.
I was thinking of getting some PUL from greenbeans and making my own version, but since I discovered woollen longies and soakers he wears those as pyjama pants and we don't get leaks.