Very interesting to read this post.
About 5 years ago I had very bad plantar faciistis in my left foot. Cured with with self-treatment using exercises and advice from internet.
Almost 2 months ago I suddenly felt pain behind my left ankle walking downstairs (I hadn't injured my ankle in any way). After a couple of weeks I then had pain in my left calf after walking for, say a mile or two (I was covering about 20 miles a week rather than using the bus) and wondered if it was a circulatory problem because after a brief rest it went away but then came back on resuming my walk. Eventually because this was interfering with my life so much I went to GP, one who didn't know me - it's years and years since I went to GP, my designated GP from years ago had left and my new designated one on leave. I suggested Achilles problem, he didn't think so, he emailed me exercises for an injured ankle (I told him it was not injured). I've done them faithfully but no better. I'm sure it's tendonitis. I'm also getting regular night cramps in right leg, really painful. Sometimes left ankle hurts when walking, sometimes shooting pain and left knee aches a bit, sometimes aches in bed but sometimes left leg feels better. I definitely think it's achilles tendinopathy and I need to contact GP again - might ask for a second opinion.