i will address your last question first.
To complain to the surgery, it is best you do it in writing to the practice manager in the first instance. Hopefully this will bring local resolution of the problem. You might like to copy in your local pct complaints manager too.
As to your first question -do i have a legal case? A legal case for what? as far as i can see from your accoubnt the practitioner hasn't actually harmed you in any way, just given you (in your opinion) duff advice. Medical opinions do vary, and it was completely your choice to go privately. Do you really want to spend thousands on solicitors bills in order to be compensated a tiny amount (if at all?)