The reason Bournemouth came very close to having an exam centre is because the three schools located there all argued (with the CAA) to get one. The reason the scheme failed has already been discussed in this thread.
If the CAA receive enough logical arguments for a centre in the midlands (or anywhere else for that matter) they will look at the matter and may well agree to it. But without the active support (agitation) from at least one school, the CAA are unlikely to be swayed.
Distance learning (by definition) involves studying at a distance. For a good many non-aviation types of distance learning courses this means distance both from the school and from the examination centre.
All ATPL distance learning students are required to travel to their schools for the consolidation phase of their training. If students carry out their consolidation immediately prior to their exams they can stay in the same area and avoid additional travel costs.
It is also worth noting that one of the schools that supported the establishment of an exam centre at Bournemouth provides only distance learning courses. That school clearly recognised the value of having an exam centre in the area where students carry out the consolidation element of their course.