Cigarette smell

[MrsG]

I’m buying a property from a smoker and it reeks of old cigarettes. My husband and I have never smoked so need to get rid of the smell before we move in. I’ve been told the best thing to do is seal the smell in with oil based undercoat on the walls, ceilings etc. we’re ripping out all the carpets and replacing them so can paint the floor too. I’d like to know from someone who’s done this whether a deep clean beforehand will suffice. I’ve read about chemical wash and fogging and ozone treatments but they come in at £3000+ and as this is a ground floor maisonette I’m worried it will penetrate the flat upstairs. Any advice gratefully recieved.