In reply to mark_wellin:
Thank You All. I'm pretty sure it's one of the bicep heads. With my elbow held at 90deg I get a twinge rotating my fist outwards against resistance (nothing in the opposite direction). Does this suggest one portion of the bicep or another?
I'll add the bicep negatives to the hammer rotations I've always done - thanks for that one.
Muscular imbalance - 15 years climbing, I've absolutely no doubt. Could anyone recommend a good physio in the Midlands who understands climbing?
I've been laying off the climbing but of course real life doesn't stop and recently moving house (and it's contents) has hardly helped!
Thanks again for all the advice - I think the rehab deserves the discipline of the climbing.