Hi,
First, I can not believe that it is possible for a GP to send this type of message. No comment. HbA1c is the average of your blood glucose for the last 3 months and your HbA1c is at the lowest treshold of prediabetes range, which means starting with life style changes at this stage...
I am not a doctor but from my knowledge maybe you want to contact your GP and ask if is any probability the headaches after eating are related to the bile? I had a similar situation and I was told it might be that.