I think it definitely depends on what the au pair is doing and their experience. We have a lovely 18 year girl starting in September with no experience. She'll be with us for 6-8 months. Her main tasks will be getting our 2 year old son ready in the morning and dropping him off at the childminder (9am) and then picking him up at 5.30pm until we get home at 7ish. She's practically free all day to explore the city, take on part-time work if she likes (prioritising us of course) and do a language course etc. As such we are paying her at the lower end (?75) and she's happy about that. Not to mention everything is naturally covered by us from food, toiletries, travel, flights home including Christmas, phone etc. She's only doing the drop off and pick up and her hours are likely to be max 15 hrs a week. Anything more seems unreasonable in our situation. If she was looking after our son most of the time and/or doing after school care etc we would certainly pay more and I think ?100-120 sounds very fair for the added work, particularly if looking after two or more children as well as no other child care costs involved.