Day 2... Second anonymous answering message. -_- I can't even call them back, because they've withheld their number - not that I want to, I'm spending a fortune calling people and explaining that "no, she doesn't live here any more, what a surprise she didn't tell you (not)", and it sounds like it's only some foreign telemarketing agency. (I hope - although still, how DID they get my number? And more to the point, why have they connected it to HER? And I hope they're not affiliated with anything more serious - it sounded like an Indian callcentre, and I'd guess a debt collection agency )
...I'm going to contact the Telephone Preference Service. -_- I'm registered with them, and their website states "it is a legal requirement that companies do not make [unsolicited sales and marketing] calls to numbers registered on the TPS", so maybe they can do something.