Yipee. Just got back from seeing my GP. I went with a list of symptoms that haven't improved since my loading doses 12 weeks ago. He was interested in the BMJ review paper I gave him and decided that my neurological symptoms had got worst since I was first diagnosed.
He's agreed with me that I need tests for MMA and holotranscobalamin as well as thyroid hormones. He's going to refer me to a haematologist and he's given me prescriptions for Gabapentin (for the needles in my toes that keep me awake) and for Hydroxocobalamin ampoules sufficient for me to self-inject once per week.
There are some doctors out there willing to listen and learn (he didn't know that active B12 tests were available). I feel so lucky to have one.