I booked (well in advance) wheelchair help for my Mum (traveling l/h on her own) a few months ago. Total waste of time since we arrived in good time for her to be taken through security but there were not enough staff to deal with the demand. Given that all of the people there were pre-booked this was unacceptable!
So she took herself through security and thankfully got on her flight. Next time I won't bother. I'll just book a fully flex somewhere, take her through, get her on the flight and then offload myself and go home.
Whether it is BA or BAA it is a rubbish service that is offered and it needs sorting!