soon: I'm guessing it must be light wetters that can cope with not prewashing the UDs. Only part of the nappy was wet, so was really like it needed breaking in and was just tooo new to absorb a BIG wee so quickly and it just poured out the nappy instead! Benjamin can empty his 8oz cup quite early on in the night, so really does put a lot out, I think! In any case, I got my pre-loved WNNNs today, so he's in one of them tonight. I think one is cotton outside with hemp inserts, and the other is all bamboo. So, have tried the bamboo one tonight (as not really used hemp much yet), so we'll see how we get on. I know Fiona at UD told me it probably only needed a couple of washes to be at full absorption, but perhaps the problem is that I didn't dry them at all between the two washes.
So, will let him wear them during the day tomorrow and see how they work before washing again & trying for a night. And will report back again, I hope! (tho having to sneak on my husband's computer, as my laptop's cooling fan has died and having to wait for one to ship from Hong Kong!)