I think you have 2 different answers depending on what you want. If you want to join the standard brush-up course of another distance learning groundschool then Bristol are undoubtedly excellent, I can only suggest GTS as another alternative. Although we can do so at BCFT we would probably have to put a course on for you specially as we are quite recent on that side and our distance-learning students are not yet at that point.
On the other hand if you want your own brush-up tutors, one to one, then I'm not sure Alex has the spare capacity to do so. We have at BCFT, as have one or two others (Oxford used to I think, and you might try GTS). Not sure who else, this is sometimes difficult to find, so contact a few other groundschools.