In reply to climbercool:
I've been waiting over a year for ACL reconstruction on the NHS. I've seen about £7.5k quoted for private.
My knee currently feels very stable; I can carry heavy weights, ride bike, etc., but I haven't done any running/twisting on it.
The advice I got from the specialist was that if I just wanted to run and cycle I could probably treat conservatively, but if I want to get back to bouldering, heel hooks, drop knees, etc. it would be best to have the operation, and to avoid any running/twisting till the op to avoid any further damage.
It was the falling from height bouldering that particularly concerned them.