The government's own figure on cost to NHS of smoking related diseases is between £1.4 and 1.5 billion.

http://www.hscic.gov.uk/catalogue/PUB11454/smok-eng-2013-rep.pdf

Other research estimates it to be much higher, depending on which report one reads, anything upto £5 billion.

One figure that cannot be disputed is that tax revenue from tobacco products is currently over £12 billion pa and rising every year.

http://www.the-tma.org.uk/tma-publications-research/facts-figures/tax-revenue-from-tobacco/

Whatever our views on the subject, it's not very fair to say smokers are a drain on NHS resources, they are clearly self-funding.

It could be argued that they help to subsidise  the non-smokers.