Empty legs seems to be the only way us mere mortals could ever afford to charter and to be honest I struggle to understand the appeal.
As far as I can tell, I would have to scour the web and if I'm lucky, there may be an empty leg come up around the date that I want going to the place that I want, however it is unlikely I will get a return and you are at the mercy of the individual that made the original booking so could be left high and dry if they cancel their trip on the day for example.
Also planning my trip around the flight defeats the object of charter, the flight should fit in with my needs... So until I can afford to charter myself, it's British airways for me... Unless I've missed something glaringly obvious???