flower, sorry if I was being thick, but your point wasn't obvious to me. I thought you were questioning the merits of climbing in to the TMA but you also said "I understand in an emergency you will do whatever is needed to survive and quite rightly so ". I thought you were warning of a problem with doing so, but now I see that you're actually saying don't do it. I'm surprised by this. As per other advice (or even regardless of it) I'd be squawking mode C, in contact with Thames Radar. I'd like to think that I'd get the Mayday call out pretty quickly, especially given the scenario, but likely not before making that climb. If I was on my own I'd certainly probably never get around to setting the mayday transponder code, though if I was with a passenger I might, but even then, not before climbing.
I don't underestimate the outcome of hitting an airliner, but with the things I've already mentioned (radar, their TCAS and my eyes) plus the big sky theory (albeit with us in a small part of it) I'd (instictively) give myself better chances of survival with say a 500' climb from 2400' and taking that risk of a collision. What do other people think? AlanM, how much traffic am I likely to find on that crossing at 2900'?