... I am to have another op! I won't get my leg straight again but the doc is going to give it another go. ... I am to have an epidural, then the rugby team (physio) will come in and jump on it for a 4 day hospital stay. If it does not work ... big decision... revision.

I don't understand this. Caveat: I have no medical qualifications, so perhaps there's no reason why I should understand, and I hesitate to raise a question for this reason.
So am I correct in saying they are proposing not to open you up, but another MUA? Fair enough. Thereafter the BoneSmart mantra will apply and lots of lazing around will be appropriate.
But number 1; then revision if that doesn't work? I thought that revision is only if the joint itself fails or has been installed so badly that recovery is impossible, neither of which seem to be indicated here.
But number 2; you're only a short way out of your first MUA and you say yourself have been overdoing things. Wouldn't waiting awhile be another approach? You say you won't get your leg straight again, but then if it's swollen to twice the size it should be then you wouldn't anyway until that swelling has gone down.
You are no doubt big and strong, and you've said you have tight calves due to all that rugby and other exercise. It strikes me, then, that it might well take you a long time to stretch the tendons to get your leg straight, and that (as you've also said) your body might resist more than a normal person's.
Now I've stuck my nose in here where it doesn't belong, I invite
Josephine and
Orthodoc kindly to cut it off if I'm talking nonsense again.
Thank you to all for help and advice. Really needed the advice and thank you all for the continued support. I hope I can pay it back.
This place is great isn't it? I got huge help, which can never be paid back IMO -- but it can be paid forward by offering experience, help and advice on here to those following.