Well, I have prediabetes, and I'm 5'10 and weigh 10 st 3 lbs (according to converter), go figure. Both the literature and the diabetes specialist, I just saw, say that some people just have fewer betacells to begin with. Betacells are the cells that make insulin. And when they get overworked from insulin resistance in the body and too many carbs in the food, they start to die off.
I would recommend that you cut carbs and replace them with fat, using your meter. I got very useful info from this site:
http://www.phlaunt.com/diabetes/ . I stay below 7.8 mmol/l at one hour and below 6.6 at two hours after a meal all the time, by eating less carbs. I actually try to stay below 7 at one hour and back to my fasting levels of 5-5.5 after two hours as this is apparently closer to healthy values, and I mostly succeed.
It doesn't really prove whether you are prediabetic or type 2, but from your high fasting values it would seem you have progressed to type 2. I haven't measured higher fasting values than 5.4.