I've just had an ultrasound done and they've discovered a few small gallbladder stones?

Just have it out, it's a same day surgery. If one of those stones rolls out of the GB and gets stuck in the duct that takes bile to the stomach you are going to be a world of hurt. It's like having freckles. maybe no one in your family has them but it just so happens you do...same principle here. It's too late to control your diet for prevention but you can go to a very very bland diet--no fried, fatty or greasy foods, no dairy or red meat, no spices or anything with fat in it or you can have the surgery and resume a normal eating pattern