To speak to members etc, then a local show like Enfield is better. The shows like the London Champs are very busy, and most exhibiting members will be out and about looking at the other exhibited species and stalls. There are usually many members of the public looking around the tables and a new member trying to catch someone's eye isn't likely to get noticed. It is a nice day out though with lots to see other than mice so if you do decide to go, PM me and we'll arrange a time for me to be hanging round the mouse table so we can chat. That goes for anyone else going too.
I won't be attending Enfield as I'm off to a wedding but introduce yourself to Eric and Terry, the nice guys who run the show, and they will point out other people for you to talk to as well. You could ask the judge if they mind you sitting nearby and watching. I hope that, if you go, you have a nice day.