I think smoking more or less pays for itself, cost 2 billion a year, revenue from taxes circa 2 billion.
The new culprit is obesity related diseases, which currently costs 2 and a half billion a year and rising each year.
Therefore we should really introduce a fat tax.
Simply have 3 check-outs, one for normal sized people, one for obese people, and one for the morbidly obese and tax them accordingly.
You could introduce a special dispensation for those who can claim it is glandular.
We currently live in a society where any activity considered harmful to the greater good is taxed to shit, all bar gluttony.
It's not just the health service that would benefit, we would also probably reach our desired levels of carbon emissions if these people consumed less exercised a bit more etc.
They are killing the planet and no one seems to have the stomach to tackle them.