I have worked for companies that turn a blind eye to smoking in the cab, you and your employer have to be sensible about it and i’ve never had a complaint, a fifty quid fine isn’t out the way if caught, less serious than getting caught for speeding, phone use, not wearing seat belts, jumping red lights, bridge bashing, fiddling tachos, running over weight etc, bet there are a few non smokers who have been caught for some of those offences, but then get on their high horse because some one else has broken a law!
And then there is nothing worse than an ex smoker complaining about smokers.