During the summer I try to do a lap of Rutland Water at least once a week, always good fun and a good way to keep fit.
Well done for managing 18 miles after such a long time, the trick is to keep it up and it'll get easier with less pain. Where did you cycle?
Rutland Water is fairly flat with a few hills, 17 miles takes about an hour and 20 minutes, but this summer I'm hoping to get that down by 10 minutes. There's also a slightly longer course at 24 miles - well worth it for anyone in the area.
I have a Specialized cross country/mountain bike, but I'm not sure of the model, Hardrock pro disc rings a bell, but I've had it a good few years.
If anyone fancies a meet and cycle at Rutland Water this summer give me a shout.