Well... I've got the game flyable(ish) now and, when it is behaving itself, I am getting slightly better fps.
The biggest problem is stability in that I am still getting heavy fps loss with clouds (Only when flying through them... but it was like that for me pre-alpha so...) and particles... in fact much worse since the patch, I've now had to turn grass off (Which is a step back) and I'm getting the disappearing and reappearing tree problem. Can't remember who mentioned that the cure for the trees was leaving the game and going back into it again? That definitely works at first but if I fly, for instance between Pihen and manston, I find that once I cross the channel all the trees have vanished again and, obviously, leaving the mission and restarting isn't really an option so I end up with a very boring landscape. I've also encountered incredibly heavy drops in fps (Down to single figures) over the channel which is odd to say the least.
Still not entirely convinced by this patch....