Was your flat built or converted since 1992? If so, might be worth looking into whether the soundproofing complies with Part E of the Building Regulations 1992 which says that "floors and walls between domestic buildings should have a certain resistance to the passage of sound" (new, stricter regulations are coming into force in July 2003, but this doesn't of course help you). I don't know what the cost is of insulating your floor, but you might think it worth getting the advice of a surveyor/architect type person to see if your soundproofing is adequate (probably cost around �100 or so). You might then have a claim against whoever built or converted the flats. In the meantime, don't go ahead with insulating your floors until you've looked into it further. It's a bit of a long-shot, but have a look at your buildings insurance policy and see if you could claim under that (e.g building defect).