Thanks for your replies. I'll keep up with my routine and post any changes. Bike fit is ok, maybe not great, but I will have that looked at before I start doing longer rides. I think I'm too stretched out at the minute, which could be what's causing the arm and shoulder pain. The solution, I'm told, would be to stretch the back and glutes and lean forward a bit more. I'll work on doing that. In the mean time I have a shorter stem I could attach. Does that sound like a good idea or would I just be referring the strain to another area?