Hamstrings have a dual function of propulsion and stability; every hamstring problem i've ever had that wasn't down to slipping on ice or something was later found to be part of a larger landscape of stability issues. My gut instinct would be that the physio is right about its origin being stability, but the approach to recovery is obviously not yielding results. I have similar pains to you that have been attributed to bursitis. I'm throwing a lot of anti-inflammatory cream at my hip, and doing the swastika stretch, but a pigeon will do. Obviously i've also quit running for as long as it takes; this is the part most people don't want to do.
Luke Appleyard (Wharfedale)- quick on the dissent