Slots at Gatwick - not easy but not a problem!
Right between SA and UK - no problem for an SA based carrier - the current billateral allows for 42 weekly freequencies by each country, UK is using all (at least during summer) and SA is using 24 (maybe 27 during summer)!
Leasing a 777 from BA - non starter since they are short of long haul capacity, they are even considering using 757s transatlantic when open skies begin!
Comair's appetite for long haul - not a chance!