I don't think it is so clear cut any more. Probably since more people started going to university, which opened up professional jobs to people from wider backgrounds.
Plus conversely, in many parts of the country, even two low to medium professional salaries, eg up to around £50k pa, don't buy typical middle class housing without significant parental help or inheritence, or until much later in life. So you might have well paid professionals renting, while manual workers in cheaper areas buying their homes.
All my older male relatives were miners. Women tended to be SAHMs or did bits of low paid part time work like retail, hospitality, cleaning, although DM passed the 11+ and went to grammar school, then went to work in a bank, but she stopped working when she had me, as was the norm at the time. But my parents and many like them bought their own home.
We are definitely traditionally working class, but with many of what are usually deemed as middle class signifiers like we saved for things we wanted, rather than taking out credit, we went to the library and museums, were always given books. Education and cultural interests, history, visits to National Trust places etc were seen as important, but then I'm still the only member of my family who's been to university.
We didn't have foreign holidays, but when I go abroad now, I'd choose a cultural city break or a traditional, quiet authentic place over something like All Inclusive in Benidorm or Magaluf.
In these threads there always seem to be a lot of people saying 'I'm middle class and I'm not like working class people because I value education and quality over quantity, but in my experience a lot of the 'class markers' apply equally to all types of people of a variety of backgrounds.