A conference I'm working on currently is looking for a suitable restaurant/private dining space to host the speaker/VIP dinner the evening before the conference. Previously we have used Kettner's and Beach Blanket Babylon (Notting Hill). It's for around 35-45 people.
Most people will be staying at the Montcalm at The Brewery to give an idea of location, but we usually order a fleet of taxis to ferry them there and back. So as long as it's not hours away, distance shouldn't be too much of an issue.
Oh, the other thing is that it'll be on a Sunday evening.
As someone who doesn't live in London, I'm struggling on this one!