Yes: Comair operates under two brands. It has British Airways liveried aircraft operating franchise services for BA, which are very similar to mainline BA flights, and (as you have seen) it has a low-fare airline brand called Kulula which has its own (distinctive) livery and sense of humour.

If you book through the Kulula website, you are sometimes offered British Airways flights on BA flight numbers - booking these will simply get you a BA booking in the same way as if you'd booked via ba.com. However, there is no way of booking Kulula flights through ba.com.

ISTR that Comair operates both brands on the same AOC, so once in a while there will be an aircraft swap in one direction or the other. A couple of years back, I booked a Kulula flight from DUR to CPT but Comair subbed in a BA-liveried aircraft. Three days later, I flew back to DUR on a BA ticket and ended up on the same aircraft.

For collecting Avios when flying Kulula, you might want to have a look at these pages: http://www.kulula.com/flights/avios and http://www.avios.com/za/en_za/collec...flights/kulula - but I have no idea whether these would work with a UK avios.com account.

I know people who've been admitted by the SLOW lounge when flying Kulula on the back of a BA Gold card - but we don't fly Kulula enough to know whether one could rely on this.