Hi Ziggy,
I'm not surprised you were taken off the Diamicron because that is glicazide and you shouldn't take a sulphonylurea like glicazide together with metformin and insulin. To convert your mg/dl measurements to the mmol/L that we understand over here, just divide by 18. Your 200 mg/dl equates to 11.1 mmol/L, which is high but not earth shatteringly so. Like you I pigged a bit yesterday on a rich dessert and my BS this morning was 277 (15.4 mmol/L). Unfortunately I can't bring it down rapidly as I am not on insulin, so I will just stick to low carbohydrates for a couple of days until it normalises.
When your doctor told you 10 to 20 units, did he give any instruction on what situation you would need to increase the dosage and how much to increase it by? If you are intending to up it to 12 tonight then presumably you have been on 10 so far?