It might well work out cheaper to book the flights separately.
According to the website of Charlotte-Douglas International Airport, there's plenty of competition on the route from Orlando, so fares should be quite low.
Airlines operating on that route are listed as
US Airways:
http://www.usairways.com/
AirTran airways:
http://www.airtran.com/
and United Airlines (operating under a code share arrangement with United Express):
http://www.ual.com/
However, the Charlotte-Douglas website states that US airlines operates
direct flights from Gatwick. I'd recommend checking out their fares before booking a two-leg flight.
Chris