If a group of people who are smokers wish to hire or use a licensed or unlicensed premises indoors for the purposes of recreation they should be allowed to do so. It is a basic human right of association.
I suggest that local authorities can have a quota of premises (dependant on the population of that local authority area) that can be granted conditional indoor smoking permits. Certain public houses that have met basic air quality conditions and are able to seperate non smokers from smokers (or be closed to non smokers) should be able to apply for such permits for certain advertised events organised by smokers.
I would recommend smokers had to pre-register and become members of such events to obtain admission to remove the risk that a non smoker inadvertantly entered such a venue or event.
Staff working at such a premises must sign a waiver wherein they confirm that they are either a smoker themselves or that they waive any right to protection under the public health act, much in the same way people can opt out of working time regulations designed to protect the health and wellbeing of workers at present.
Why does this idea matter?
If it is legal to buy tobacco it must therefore be legal to enjoy tobacco. The public have a basic right of association and this right is removed for law abiding persons who happen to smoke. The blanket ban in the UK is detrimental to the public houses many of which have lost their regular customers to off licenses. Other European countries are able to protect and promote public health without a blanket catch all ban that is deeply unfair to people who are smokers who have the same right to enjoy going out for a drink as anyone else.