I won't be able to attend the blade meet on Beyday, but I'm definitely up for the summer meet.
Location wise, how about Regents Park? It's easily accessible from just about any direction, it's right next to London Zoo, and there are multiple heavily signed meeting points within the area.
It's a 9 minute walk from Camden Town Station, and 2 minutes from Baker Street (although Baker Street is on the other side of the park.)
I was thinking Ready Money Drinking Fountain would be a good meeting point, and there's a nice cafe that isn't ridiculously over priced in the park called The Honest Sausage that we could go to after for a coffee, fruit juice, soft drink, beer.etc
Sorry if I just butted in there, just thought it'd be a nicer place to meet than the Excel center, which we'll most probably be removed from since they'll have other events going on there.