You do not say if you are cc or flight deck, but the rules applies to ALL, not most ! Get yourself a copy of Flight Crew Orders, or better still the CAA ANO's, and then see if your colleagues are aware of the requirements. I sat in Club a while ago whilst taxying out on an ATL flight listening to a cc dscribe how they had diverted to Stansted yesterday on a back to back, got transport back to LGW by late pm but still checked in for 9 am check in. By my calculation they were way out of duty hours, but their topic was the extra money involved made it all worth while. With the BA system I doubt the Captain was aware of his cc hours.
If you are retired BCal/BA crew as you state, you will know that the crew can not and do not operate from base without a minimum legal rest period between flights. The flight is automatically recrewed. We don't even get a say in it and you can be sure ops would have known pretty much exactly what time the crew made it back to LGW as we have to sign out on the computer system. Even without the computer, they'd have the times from the transport company. But like I said, you don't need me to tell you that as you'll already know.
Apologies for the thread drift as this isn't even related to commuting, let alone the dispute, but I will not sit back while someone implies that we are flying illegally.