Woah. Some of these answers are ridiculous!
Cutting managers?! Are you crazy? You cut out the organised part of an organisation and it will become anarchy. Cutting managers will create far more work for others. In my current job I deal with a lot of service managers within the biggest hospital trust in the country and I can assure you that my job would be virtually impossible without them.
Smoking age is already 18, so that point is nullified.
Cosmetic procedures are mostly done through private practices now, so that point is also pretty irrelevant.
Cutting pay will just lead to mass emigration of doctors, as we are currently seeing with emergency doctors leaving for Canada and Australia. The medical training in the UK is second to none, but if people can't see any benefits beyond the training, their skills will be just as good elsewhere, and they'll have a nicer life!
It's hard to pinpoint individual areas to cut directly. It's more the knock on effects of other policies that will have the greatest influence. Making alcohol much more expensive to buy would significantly reduce teenage alcoholism and the binge-drinking culture this country is infested with. Same goes for cigarettes. In my hospital trust they are about to completely ban smoking in any area on hospital grounds. How strictly that will be enforced is another issue, but the thought is there at least. I believe investing in public health and in health education will be very important in reducing costs nationwide, but I'm no expert on this and can't really offer any specific suggestions.
I believe privatisation of elements of the NHS could work. Around 90% of ancillary staff and privately sourced, while admin and clerical staff are also often sourced from private agencies. This is fine for non-medical staff as their roles don't require as much working in a tight team, lengthy training, knowing each other's strengths/weaknesses etc., but I believe it's better to keep medical staff predominantly on a more permanent basis, employed by the NHS. However, saying this, this probably won't reduce costs that much.