There's certainly a gap in the market for Hannover in the greater SouthWest.
Whereas various airlines fly from Bristol to Hamburg, Bremen, Berlin, Dusseldorf, Frankfurt and Munich there is no service to Hannover.
Slightly surprising because Hannover is one of Bristol's twin cities and has been since just after the end of WW II, and there is still a lot of interaction between the cities socially and in commerce/business.
Those to the east and perhaps south of Bristol might find SOU reasonably accessible but EXT would be easier to reach.