In my view, you will not be able to have the diagnosis removed from your records, unless the bloods were actually below the diabetic thresholds, at diagnosis. the only way you would know that is to ask for a print out of your from your date of diagnosis, until now.
From my personal experience; I was diagnosed on one set of bloods, and since then, my bloods have all been in the non-diabetic ranges. My stats are in my signature.
During a discussion with my GP, about something else, we entered into a discussion about when I would begin to get some credit for reducing my bloods. By that I mean, and more moderated view on "all diabetics x, y or z", with no recognition of my current decent blood state. At that point an agreement was reached that I should be recorded, on my records as "Diabetes Reversed".
The diabetes diagnosis meant my body was behaving as a diabetic at the time of diagnosis, but now I have been fortunate enough to have coaxed my body to revert to a more normalised state. The diagnosis is a statement of considered fact, on that day, on the evidence before the Doc. After all, one wouldn't challenge a diagnosis of chickenpox a couple of years later, just because the spots had gone?
As a well controlled T2 diabetic, the implications for insurance and so on should be minimalised, provided you state your case clearly to insurers. It may mean a bit more explaining that someone who has never been diagnosed. There are some classes of insurance that might be a little more of a challenge, but the fact you have has a series of non-diabetic tests is in your favour. If I were an insurer though; and I make this statement as someone who has worked for a major Life Assurance company alongside actuaries, underwriters and pricing analysts (those who make the decisions as to whether an individual is a decent insurable risk, and what any premium might be), you will not have done yourself any favours for not having all the associated checks, on your eyes etc. That could be viewed as non-compliance on your part.
For travel insurance - even longer term, long trip insurance (longer than 90 days duration), I h ave never, ever had any premium loading or exclusions, so I wouldn't be too concerned about that aspect.
I would say you should get your blood results, if you have any intention of properly challenging this. I would say, if anything, you have a far better change of having yourself reclassified as Diabetes Reversed, or In Remission - whichever terminology your GP might see fit.
Of course, that's probably not what you want to hear, but I have tried to address your apparently underlying concern from both a diabetic and insureres' standpoint.