I've lost about half a stone now basically by eating and drinking a bit less and exercising a bit more, and it feels good! My BMI is still around 27 though so I've still got a way to go before reaching a 'not overweight' 25. It would be easier if I hadn't shrunk from 5'6" to 5'5" over the last 10 years! I'm also not sure that BMI is a realistic measure, as it doesn't take into account your muscle weight.
In terms of diet I've been loosely following the ideas of the F2 high fibre and Gi Plan diet, which seem healthy in that you fill up on fruit and fibre and keep fat intake down. I did consider the Dukan diet but decided it was crazy and unnatural. The only real modification to diet though, apart from eating a bit less, is that I have added a grapefruit drink or half grapefruit for breakfast and I suppose we eat a bit less meat and more salads. I already was eating plenty fruit, veg and fibre.
My exercise consists of cycling to/from work usually 3 times a week with one swim, one or two gym sessions and sometimes a 3 mile run. Then at weekends I usually go for a short or long bike ride or a walk with my wife. I've also been working on my allotment which can be quite energetic.
I tried calorie counting for a few days using http://www.myfitnesspal.com/ - but probably won't do this regularly. It does however give you an idea of how much food and exercise you need to do to reach a target weight in a number of weeks.
I'm not sure if I'll manage to get much below 11.5 stone, but at least I plan to keep a trim waistline whilst building up my upper body and leg muscles. Hopefully I can get down to 11 stone.