The good news - the knee has improved. The4 bad news - slowly. I'm also not sure if it's eased because of my using ibuprofen gel on it to take the ache away. It's getting iced regularly (the ice pack is on my knee as I type), and massaged at night too to loosen it (although that does cause significant discomfort but it feels better afterwards.
Another thing I've decided to try is glucosamine. There are medical trials which show it can have effect on joint health, while other tests say they don't. I'll take it for a few months and then make up my own mind.
As it stands, I still can't see me running until September. As I find out in October whether I get a London Marathon place, I'm getting a little impatient. But I musn't get too impatient, start again too early, and do more damage. Patience will be worth it in the long run.