Sure, the timeframe of this particular request isn't feasible but that doesn't make the question of coming to London a moot point. You've said before that you

Sure, the timeframe of this particular request isn't feasible but that doesn't make the question of coming to London a moot point. You've said before that you would 'possibly' come to London. If you gave more info about what the difficulties are then that might either (a) help people understand why it might not be worthwhile yet or (b) what the hurdles are that local folks might be able to help with. I'm certainly willing to help out at this end (and I'm sure many others are too).