I'm working on a MG fantasy (set in present-day England) and would like some advice on how plausible the setting/backstory is. Preferably, the sort where, if it has some problems, the kind of advice that could offer a way to fix those problems.

A family called the Westwoods has lived in an old house in an out-of-the-way English town named Attenbury (in the border territory between England and Wales - definitely on the English side of the border, but still not far from Wales) for centuries; they've traditionally been among the leading families in town - and have even been expected to participate in annual events (for example - the case featured in the story - hosting an annual children's party on Twelfth Night - January 5). There's a strong sense (though not made public - even a lot of the townspeople don't know it) that Attenbury is a magnet for strange things (of the "mythical creature" variety) - and that some of the Westwoods' less publicized responsibilities may involve keeping said strange things under control.

During the 19th century, a younger son in the family emigrated to the United States, where his descendants (though now going by the surname of Briggs - one of the descendants of this younger son evidently only had a daughter, no male offspring) still live. More recently, the senior branch of the family died out, and the family solicitor, tracking down the Briggs family to the States, urges it to move to England and settle in the Westwoods' house (with a feeling of "There must always be Westwoods in the Westwoods' house" - even if the surname's changed). (The solicitor himself - a grim old man named Mr. Saxon, with a military bearing and a prosthetic right hand that he refuses to talk about - is one of the few townspeople who knows much about the town's "mythical magnet" nature, though he hasn't brought the Briggs family in on it yet - he wants to examine them first and see if they're up to handling it.)

The book opens with the Briggs family moving in, seen through the eyes of 11-year-old Jennifer Briggs (a keen would-be detective), and revolves around Jennifer discovering the weirdness beneath Attenbury's surface - especially after she inadvertently frees a mischief-making shape-shifter and has to re-imprison it or place it under control. (With the added complication that many of the townspeople aren't quite certain on the new residents of the Westwoods' house being Americans - even Americans related to the old family - and the trickster's chaos isn't helping their acceptance.)

What I want to know is how plausible the set-up (particularly the Briggs family inheriting their British relatives' house and moving there) is, and what work I'll need to do on it to make it believable.