yawn as well mranchovy but I see you joined in the debate too... ;-)
I'm discussing it because many families come on here and see this 'advice' saying it is fine (or at least stating there is no legislation to prevent them) asking their au pair to work unlimited hours.
frak - yes I probably agree with some/most of what you are saying. Remember importantly though it's a cultural exchange program. Young people from OTHER countries need to have consistency and understand what an au pair is and what it means to work as an au pair in other European countries is the same in the UK as it is in France, Germany, Sweden, Romania etc . These girls are registering with agencies in their home countries who publish that au pairs can be expected to work for 25-30 hours.
If statutory legislation does apply frak, then au pairs come under the exception allowed in NMW legislation only providing families meet the requirements of the NMW legislation. Importantly the condition "that the worker is not a member of that family, but is treated as such, in particular as regards to the provision of accommodation and meals and the sharing of tasks and leisure activities;".
My point is that if families ask an au pair to work 45 hours a week, they aren't really working as an au pair.
You've said it yourself in your last sentence. Au Pairs should be considered at par. If families consider themselves not 'at par' then they should pay the NMW as they would need to do if they were butlers, maids, gardeners etc. [and yes if the butler or gardener was treated as a member of the family exactly as defined in the exception then they'd fall under the NMW exception too].