Hello goanna, Insulin is not a magic bullet that is going to cure all your problems with high blood glucose, especially people who are type 2 diabetic. Many type 2's seem to hold the belief that if they cannot control their bg quickly, the last resort is insulin.
This is because many, but not every type 2's problem is caused by them being to a lesser or greater extent resistant to the insulin that their pancreas still produces, there is a need for you to increase your metabolism through exercise, this reduces any resistance that you may have, combine this with a improved diet containing lower amounts of carbohydrates; do you count your carb intake? Then the metformin that you are taking which helps stimulate natural insulin production will be able to do it's work.
If you were to move quickly on to insulin without reducing any resistance you may have, you would probably end up having to inject vast amounts of insulin daily, (which is also not a good thing to do, as the non diabetic persons pancreas only needs to produce small amounts on demand), and still not not archive improvements in your control.
My advice is to improve your diet and exercise, you do not need to run 15 miles a day, just walk more often than taking the car etc, and try to reduce 5 to 10% of your present body weight, most of us are over weight so it is no bad thing to try and reduce some of it. Do this and I can guarantee that by this time next year you will see big improvements in your condition.