I wouldn't go for it even if they offered it. If you've got a BMI high enough to get it on the NHS, there are a number of increased risks from the operation itself.
It does work in many cases - there is a girl in one of our local supermarkets who is, almost literally, half her former self. But I wouldn't want it for me.
As far as I can work out, you eat very small quantities of food, so it seems to me to be a mechanical means of sticking to a low calorie, reduced carb diet. I'd be interested to learn more about the diet that goes with the gastric band, if anyone knows.
Viv 8)