Paul's is okay, but the prices are a bit on the high side for me. There's Ameyzoo in Bovingdon, I was in there today and they had a nice range and the prices were quite reasonable.
Best shot is keep going to Enfield. All the shops in Herts are pretty awful in some respect or another. Don't get me wrong, so are the Enfield shops but at least the livefood is a bit cheaper there.