Where do I go from here?

[HotI]

have you looked at baby beehind covers?

[nicjay]

I'll second the Baby Beehinds covers, and also it is worth looking at Thirsties covers too

[ss_storm]

Thanks, I'll have a google a bit later tonight.

What's the best fabric to use, PUL, wool or something else?

[ss_storm]

Thanks, I'll have a google a bit later tonight.

What's the best fabric to use, PUL, wool or something else?

[~Kim~]

Maz's fleece covers are tops...I reckon a large would fit over flats for ages.

[Indadhanu]

We really love Thirsties, and Bummi's as a close second, for flat and fitted covers.
You could also try wool soakers? And I haven't tried them but I'm sure Maz's covers are great too.