I don't like walking through a cloud of smoke to get into station. It's a small station, with single entrance on this side of tracks - like double French doors, so no other alternative.
Would it be unreasonable to request Greater Anglia to mark out a hashed yellow "no-smoking" area there? It's not as if it actually provides them any shelter from the weather than standing elsewhere, and don't get me started on the litter of their stubs!
I've tried (politely) asking smokers not to stand right by the entrance, but just get verbal abuse back!