N.B. Plans at BA can and do change at short notice!! Last year's new entrants had signed up to join BA at LHR on shorthaul; 2 weeks into their course, they were told they were going to LGW longhaul....
With that in mind, the plan is for the 6 month entrants to go straight on to longhaul. The reason is to alleviate a shortage of crew on the worldwide fleet (747s etc.) that is likely to occur this summer.
I flew with a CSD a few weeks back that was involved in recruitment. She informed me that as far as they knew, 6 month entrants were due to be TERMINATED after their 6 months were up...
Now, she also mentioned the fact that that could change between now and the end of summer 2006....the bottom line is that no one at BA (including recruiters) really knows what is going to happen to the new entrants at the moment.
It's a risk those of you wanting to join BA are just going to have to take. Sounds harsh, but it's the truth.
If you want my opinion, I'd sign up anyway. This is BA, and it's likely they'll need more crew in the near future - though you'll have to accept a transfer to LGW if that is what happens after your 6 months is up (it's got to be better than being terminated...)
Good luck!