As jindabyne points out in an earlier thread, one other major British plc which faced an equally large pension problem has found a solution that is acceptable to both staff and Company alike.
Obviously not all situations are the same, but this problem was resolved with an interesting package which included a large injection of both cash and property assets plus other financial guarantees from the Company.
The final salary scheme is preserved for all current members - new starters now have a different scheme. Employees recognised a need to work longer (talking about months not years) to retain final salary benefits, but are not being asked for increased contributions.
Do not work for BA but am regular SLF on both long and short haul sectors. Clear to me, when talking to cc during flights, that the number one concern for many is pension. There is obviously no easy answer, but perhaps your TU reps could look to AMICUS, which negotiated the deal mentioned above, for some support and assistance. On the face of it at least, there would seem to be a number of similarities between BA and the other British aerospace (and defence) company.
Good luck to all.