Just remember two things before you shell out that money.
1: Its a church Hall, its not gonna be Glamorous, there won't be any birds in skimpy costumes selling stuff (Although, I wish to god there were) ;-)
2: I have a mk1 vauxhall tigra, No, I don't cut people's hair!
3: You will meet fellow amiga users, see old and new stuff and even get a cuppa ;-)
4: The venue is about 25 mins from the centre of London by train so, perhaps you may want to consider booking yourselves some overnight accomodation you can sample some of the sights of London before heading back.
just wouldn't want you to think of it as a fantastic glam event and then find that reality isn't what you dreamt it to be. I hope you will both come though! :-)