The SWs have a long history of making odd decisions about Brenda. She got terrific A levels but decided against going to university and instead got a trainee reporter job at Radio Borsetshire (BBC local radio station). Jobs like that are very hard to get and anyone who is any good would do their level best to transfer to London or another big city. Brenda just stayed put for umpteen years and then finally decided she would get nowhere without a degree. She went to Bournemouth, which has a well-regarded degree course in radio journalism, I believe. Just a few months in, Betty died and Brenda (not very plausibly) decided to jack the course in and come home. She then applied to that renowned seat of learning, the University of Felpersham, to do a degree in marketing, as radio journalism is (astonishingly) not one of Felpersham's areas of excellence.
After she graduated she took that starter job in marketing in Leicester but couldn't cope with being so far from home and Tom, so jacked that in too and went to work for Amside.
It is just about plausible that her career is finally on the up in London as her Russian chum could have pulled a few strings for her before they split up.
Felpersham definitely isn't Birmingham, by the way. From time to time an Ambridge resident is said to commute to Birmingham - I think Mark Hebden did for a bit. Elizabeth worked there for a while, too, but she lived over there as the commute would have been too much for her. I don't know the Midlands but I assume Felpersham is something like Worcester as it has a cathedral, a university, a teaching hospital and the best local shops.