Usually at the end of the interview there's a chance to ask questions to the interviewer about the company etc and I'd suggest asking then.
You could couch in fairly vague terms like "I saw in the advert for this role that you may offer flexible working. Could you give me a bit more information about that and how it would work if I was to start working here?"
There's also more detail in this link below about flexible working and it mentions you can't formally ask for flexible working until you've been at a company for 26 weeks.
So the law says that to make a formal application, you need to have been employed for 26 weeks, however that doesn't mean you can't request flexible working before that. If you want to work from home one day a week, be prepared to compromise. Don't just say what you want.
One compromise could be to work in the office in school term; from home during school holidays. Or to work the first 3 months in the office (so you build relationships, on the job training, they get to realise that you're conscientious etc) then work from home one day a week after 3 months.
Offer to do on a 1 month or 3 month trial basis so that it gives everybody wiggle room; even if it's not needed.
The two people who interviewed me work from home. They also travel a bit to London and Manchester. They are in the office 1 or 2 days a week max. That's why they want me there all the time.
I'm thinking my petrol bill will rocket - it's 20 mins drive away and 40 mins from my dcs' school. The pay isn't that great and well, perhaps it's just not right for me.
Shame as there was a real positivity in the interview. They said they would consider homeworking for a few days in the interview (for the right candidate), then an hour later, they called me, said how they enjoyed the interview, could I come for a second interview but that they required office presence five days a week. Which seemed to contradict what they said earlier.
Not to worry. Something more suitable will come up.
I do appreciate all your input on this. Thank you.