Personally I find that putting on just 6 pounds in weight renders Metformin ineffective!! Watch your weight - this is probably the most important thing for Type 2's that are not on insulin.
I agree with earlier postings about porridge, pasta - add bread, cereals, fruit, cakes, potatoes, root veg to that list. They all make levels shoot up. The odd fasting is cool - but keep taking the metformin whilst you do so.
Good breakfasts - kippers or bacon (no fat) & scrambled eggs. No toast! Good dinners - steak/chicken/fish + lots of green veg (no spuds or roots). It sounds hard, but well worth it.
There is also some truth about combinations of foods. I can have a Little Chef (sorry) Olympic Breakfast every now & then (bacon, chips, mushrooms, sausages, tomatoes, fried eggs, toast) - with little effect (Metformin 1000mg morning, ditto evening) - but the same portion of chips on their own will make my levels sky-high.
Everyone is different. BMI makes a huge difference. Exercise makes a huge difference - when nobody is around try some energetic dancing to the radio/tv - good fun, and works!
Test often & take control - you'll be able to work out what works for you. But don't tempt fate with regular high carb food - it's a phsycological thing as much as anything else. Don't become too self-obsessive - worry & stress will raise your blood sugar levels.
As regards the trots with Metformin - remember that many sweeteners (not just in "diabetic" foods) have that effect - steer well clear. Food labelling - it's the carb content that is vital, and the ingredients. The nearer the top of the list - the higher the amount. Sugar content can be calculated in many ways - and can often be misleading. If the product contains fructose, corn syrup, malt syrup, sugar, lactose, gluclose - and the sugar content is stated as 4mg per 100, then it's probably wrong! And carbs end up as sugar anyway.
I can't comment on the insulin & metformin regime though.