Crikey, I wasn't expecting this many replies!
I'll try to answer as many questions/points as I can from memory, apologies if I miss anything (which, by the way, to an earlier poster, is how questions and answers work. I'm not intent on there being an issue and 'finding an answer to everything).
The artist appears to be a well established illustrator of books and original pieces of work, so hopefully not a penniless, struggling artist. She has drawn many local buildings, not just mine, and her website shows her drawing on location. She may well have drawn from a photograph, but it's equally likely she drew with the house in front of her. There isn't a pavement opposite the house or a window that the house can be viewed from and, with the tree coverage, it would very hard to do that from outside the property. I'm not making an assumption that that's definitely what she's done, but if it's a drawing from life then that's likely.
The drawing is of the house only, no other features at all. The title is the name of the house, which is the same as the area that it's in, so really very identifiable. I'm not going to post a picture of it, for obvious reasons 
The house as it currently is was designed by the original family member who owned, so I don't know whether that would mean it is my intellectual property by inheritance?
I only said I wasn't going to take the matter to court because someone suggested it in an earlier post - I haven't actually said anything about taking further at all, I was simply asking if I was being unreasonable to feel uncomfortable with it.
I can see why some posters might think I'm sitting around in my mansion, fanning myself with £50 notes and throwing pheasants at the commoners, but (sadly) that couldn't be further from the truth, haha. I genuinely don't have two shekles to rub together.