About metformin

Gliclazide forces your body to produce extra insulin. Sometimes, depending largely on what you have eaten, but also on general health and activity, you produce more insulin than the sugars in your system require and so you go hypo. Not a good idea, if driving!!
Metformin works differently. It discourages the body's own production of sugars, but only very slightly. Officially it is not possible to hypo on Met, but there are members here who say they have gone too low on it, but this is a rarity. Because, officially, you can't hypo on Met and in practice are very, very unlikely to do so, there is no need to test.
Having said all that, I would say that you should be testing your blood sugars - before and after meals to see what puts up your blood sugar and then avoid it in future. Your doctor will tell you that s/he will test you once a year and home testing is unnecessary, but this will not tell you what was wrong/right about what you did over the previous months.
So, my advice is to keep testing, but not for the purpose of driving.
Sally