I think your right about the house, from what I have seen of jonny's background his whole family is involved in finance, and he is from a well off family too. His parent's bought a large plot and built their home. The move back to Winchester was maybe to be close to his family, although most holiday's Anya spend's with her own family here and abroad.If I remember correctly, the house is owned my Nadya alone, not Johnny at all? Or do I remember wrong? She has also mentioned so many times how she wants to move to Scotland, so that could also be an issue to Johnny.
I am not sure she will move to Scotland as only her parent's are there, most of her work and friend's live nearby and would be far from jonny to see Monty.