...if I ask her to look after DD one day while I'm at work, just as a one off? My mum is going to take care of her regularly once a week but has a meeting on this one occasion. DD would be at my friend's house, friend has her own DS about the same age (both under one), I wouldn't be paying her and it certainly isn't going to be a regular arrangement. But I don't want to ask her if it's illegal!
And actually, now I look at it written down, is it unreasonable to ask anyway?
CMs can get special dispensation from Ofsted for twins. I think the rules are based on protecting registered Child Minders (who declare their income, are CRB checked and regulated, and are insured) and therefore the children. Someone can still look after the children in their(the children's) own home or casually if not for reward(which may not be purely financial, could be a reciprocal arrangement)