How would I go about a second opinion? The reason it was noticed was because I saw a different doctor. He then spoke with my doctor who agreed to do the tests to 'purely entertain his ideas as he is a new doctor.' And here we are.
Within the NHS, if you are unhappy, you are entitled to a second opinion. That second opinion doesn't have to be from within the same practise, or endo department/hospital, or whatever. You can ask to be referred outside of your usual area.
In your shoes, I'd be doing some reading into these sorts of anomolies (although I accept there may not be oddles out there), and taking a view of whom my personal "trusted expert" might be.
It was my GP who told me all these things, when I had seen an Endo whose laissez faire attitude made me want to harm him. (OK, I'm not a violent person in any shape or form, but I was pretty, jolly hacked off with him). I did a bit of reading, she made the referral and off I went to someone much more interested, although I still, at that point, didn't get a diagnosis. (it wasn't diabetes related).
Maybe spend a bit of time over the weekend having a ponder. As you are probably aware, Metformin is widely used to help ease insulin resistance in both T1s, and T2s. It seems to work very well for some T1s, although I imagine on starting it you'll want to be doing lots of testing, just in case you start to see surprising results.
Metformin is a drug that works best in a therapeutic dose, it it can take several days to start showing an impact if it's going to.
A second opinion may not change the ultimate diagnosis, but at least you will be reassured, whichever way it goes, that it's had more than one pair of eyes and one lot of grey cells coming to those conclusions. Trust in the message is very important in terms of accepting change and disruption.
Where are you in the UK?