Hi Bec! Welcome to Nappycino!
My DD2 is a heavy wetter. I ended up using just a normal PUL cover over a very well boosted night nappy. I used Motherease air-flow in a size or 2 up because of the bulk of the night nappy. I find the Motherease to be a more reliable cover as I got wicking on the tabs of the BBH PUL covers. The Motherease airflow is a snapping cover so no wicking. That worked great until she started sleeping on her side and now she wets out the side of her nappy which I still haven't solved. While many people won't use PUL at night, I have used it and it worked fine for me.