I think you guys are missing the point. Since we live in a capitalistic society where price drives the customer's decision it is not the question what you think you should earn, it is what your employer can afford to pay you.
Nurses are underpaid otherwise the healthcare system would grind to a halt.
Teachers are underpaid otherwise education would become too expensive.
Policemen and Firemen
Need I go on?
So, as it happens, FAs - no matter how important they are or how difficult their job is - will have to accept that airlines can no longer afford the wages they believe they should earn. You simply will not find any airline who pays you more than BA does on new contracts.
You have now joined the ranks of the aforementioned underpaid but very important professions. If you do not like it, there is always the OU.
And to add some additional perspective:
You guys can go on strike and the country will cope. Nurses can't, policemen can't, firemen can't... They have the really important jobs.
If the pilots or the engineers decided to strike, do you think BA would ask you to train for 2 weeks to take over their job? Again: some perspective please.