Hi Feebiecat,
It is very difficult to say what the problem is.
I think you need to do some testing because relying on your HBA1c makes management very difficult. If you buy a cheap monitor from somewhere like Asda then you will have a few strips, (maybe 10) to help you. I have seen offers there for £4 for a monitor.
Are you portion controlling the GI foods that you are eating? Some may spike you and will have to be reduced even further or eliminated from your diet altogether. Some diabetics can eat a small portion of potatoes, I cannot, I can eat bread, they cannot. You really have to test and see what spikes you.
It is interesting that you low carbed without testing. Low carbers are different in their response to some foods as well. You may have been having spikes then and not known about it.
Hope this helps.
Catherine.