It does seem odd doesn't it? It makes me think they'd be the kind of backward organisation which does everything the same way they have done for the last decade, because that's the way they do things. I used to work in a place like that, it was a nightmare!
They are allowed to ask so long as they are asking this of all applicants, and not just the female applicants. I imagine they do so because some people probably apply for temp jobs before lining up childcare, which would create a nightmare for most temping agencies because so many jobs are of the type where you are phoned on Friday and told to start on Monday.
Wrong. They are allowed to ask it if they ask it of everyone. They are NOT allowed to use it to favour one candidate over the other, and they are NOT allowed to only ask female candidates. It is of course a very silly question for a potential employer to ever bother asking because it suggests that the answer may lead to discrimination, but it is not illegal to ask it. If you disagree please show me the statute, as this is news to me