@LionChild it is possible you were losing weight due to your high BG rather than the keffir that you were eating.
You mention you were being treated by the district nurse but now being passed back to your GP. I would strongly recommend insisting on being seen by a dedicated diabetes team as most people with type 1 do.
A dedicated diabetes team is likely to move you off fixed insulin doses. These may have been popular 20 years ago but for the last 15 years, at least, the "basal-bolus" regime has been usual for people with type 1 diabetes as this allows you to adjust your insulin dose according to what you eat rather than having to eat to maintain your BG.
This will mean more injections (every time you eat plus one more) but the flexibility and control is much much better.
Good luck in your continued diabetes journey. There are many of us around (not as many as there is with type 2 but still plenty to assist) to ask questions.