Metformin will not have any affect on your post meal numbers, it works by limiting the amount of stored glucose released by your liver and helps a little with your insulin resistance.
It will not remove any sugar from your blood once it's in there, for that you would need to be on insulin or one of the other more aggressive drugs.
You can take metformin at any time that suits you, the advice though is to take it with food to avoid or lessen any possible gastric side effects.
The crumpets, bread, and wraps will almost certainly be why you are seeing high post meal numbers.
Carbs when digested will release glucose and cause your blood sugar levels to rise.
Your body can't tell if the carbs are wholemeal, brown, organic, gluten free or even sourdough, all it can see is the carbs.
Sugar is just another form of carbohydrate, 1 teaspoon = 4g of carbs
If you check the nutritional info for your sourdough crumpets, I'm guessing they are somewhere around 20g of carbs each. So 2 crumpets = 20 x 2 = 40g of carbs, or the equivalent to 10 teaspoons of sugar.
Check the total amount of carbs in everything you are thinking of eating and work out how much sugar you are about to eat.
The decision to eat it or not it is or course yours, but at least you will know why your blood sugar is high