It’s second hand smoke so I’d look into whether they are causing a public nuisance in the same way that smoke from a garden fire or a BBQ is if it’s frequent enough.
Councils must look into complaints about smoke from premises that could be a ‘statutory nuisance’ (covered by the Environmental Protection Act 1990).
For the smoke to count as a statutory nuisance it must do one of the following:
unreasonably and substantially interfere with the use or enjoyment of a home or other premises
injure health or be likely to injure health
If they agree that a statutory nuisance is happening, has happened or will happen in the future, councils must serve an abatement notice. This requires whoever’s responsible to stop or restrict the smoke. The notice will usually be served on the person responsible but can also be served on the owner or occupier of the premises.
Speak to your council.
Either that or rig up an IR sensor to switch on a fan blowing over jeyes fluid (or anything else fairly stinky) whenever they’re standing outside.
edit: The above are only applicable if speaking to them does nothing.