The hardest part of the whole thing for me was the depression (more sadness and anger) at not being able to do what I'd done for years. Every time I tried to start training again, I'd get a good week in and then bam it would flare up- wait another 6 months, same story but each time I got all excited. Nowadays I'm aware that if it goes, it is going to be a long lay off, and that's the thing with a chronic injury that recurs....it doesn't mean you have to quit doing what you love, but it does mean you have to re-evaluate things so that your morale isn't destroyed if it goes again and again and you just end up being thankful for what you can do.
Like you've been very similar Luke, comebacks and then lay offs- but in a way it makes the time you can run or are running more beautiful?
Cross training helps- I do a lot of weights work now which I would say you could hit real hard- core and upper body and as long as you don't overeat to bulk, your running will see some definite improvements. Use a bike or swim, and that way you are less tempted to come back early and risk reinjury.
All the best