Yes, the stable had moved to Cheshire by the time Amberleigh House ran. Must have been some time in the 80s or early 90s I would guess. I remember seeing a part time job advert for them during the 90s and they were based in Cheshire then.
I do recall some mention of a half brother to Rummy at one point, but never heard anything further of him so certainly didn’t have Rummy’s ability.