Good idea about the temporary heel lift - remember Gradual Progress. There’s an old saying in the UltraLadies’ group (a group of female ultra runners) - you know you’re an ultra runner when you wear high heels to relieve your achille’s tendonitis. Seriously, it sounds like you are on the right path with your physio. As you learn to relax your lower legs, you’ll be able to let your heel make contact with the ground as you ‘land and load’. I have the same issue in my right leg, due to a combo of biomechanical issues and life long habits hard to break, and when I feel my heel talking, I do the heel drop exercises on the step of the stairs. Keeping only your forefoot on the step (and holding the rail for balance), slowly drop the heel down below the level of the step, then slowly raise up on your toes (like a calf raise). Repeat that slowly, working up to 30 reps. For me, it works like a charm as it gives my tight soleus a slow stretch and relieves tightness all down the chain to the foot.
Mel - work on the core stability! It pays dividends in making your feet feel better!
Certified Chi Running and Chi Walking Master Instructor