My lower back was the main problem. I do get a sore back from time to time, but read a lot about it and it would seem a road bike does not necessarily exacerbate a sore back.
However, clearly my posture is wrong or something, cause that was just all wrong!
... I hope. I can't help but think if I'd jumped on a new Giant hybrid with front suspension I'd be feeling happier just now. Not necessarily in a few months of commuting, but tonight, yes.
(I thought my wife was going to burst me after listening to me bang on about a new bike all summer. So, did you have fun on your new bike? ... Eh, what do you mean, you wasted £1200?????
Bad times.