Just to put in MTPW.
You do not need a PPL for the bmi british midland or BA sponsorship scheme. In fact, you don't even need any flying at all for BA, whereas bmi do prefer 'some experience of handling light aircraft'.
On another point, I would say that you would be in for a very hard time at the bmi sponsorship interview if you had not read 'Handling the Big Jets' or 'Flying the Big Jets' from cover to cover at least once. Their interview is totally different to BA as they will quiz you in depth on the technical aspects of general and commercial aviation.
Regards
Barney