You can probably get a good fare routing over London Gatwick between Continental and Ghana International Airlines. The airlines have co-ordinated schedules and interline passengers on the route. A number of passengers used this route last summer due to pretty attractive combined fares. You will probably need to go to a travel agent though to book this kind of itinerary however.

(Disclaimer : Please note that I have an existing relationship with the carrier in question and accordingy my reccomendations are probably biased.)