I don't think I need any advice about employment law thank you. Seems pretty clear to me...
'This Agreement will form part of the crews’ contract of employment and will supersede the limits and definitions in the OPS General/Basic manual Section 7, Cap 371 and the ANO. Where items are not covered in this agreement then the limitations and definitions laid down in Section 7 of the OPS General/Basic manual, Cap 371 and the ANO will apply. This agreement will be subject to seasonal review.
No changes will be made to this Agreement without prior consultation and Agreement between the Company and the BALPA Company Council."
This is not BA, but another BALPA recognised UK operator. As per my previous advice, I would check your facts before talking about deals being signed and sealed.