Any airport within a couple of hours or so drive from London has a number of challenges to overcome, arising from the proximity of the London hubs.
The link below takes you to a well researched CAA report on the draw of London. If you want to understand how the airports and airlines business works in the south of England, this will help.
If nothing else look at the easyJet chart on page 59.
http://www.caa.co.uk/docs/78/rpt%20s...on%20final.pdf
Bournemouth has an excellent catchment, its feeds Heathrow & Gatwick very well, and Flybe does very nicely from it at SOU. Things are unlikely to change much. This also demonstrates the reasons why Flybe are interested in London City.