My sister in law worked at BA for two decades - I think she was given something like 4 transferable FREE seats a year, plus any number of heavily discounted seats.15 to 14, in line with most other carriers I believe.
Quite where this idea that cabin crew only get to fill empty seats comes from is a mystery, I know plenty of people, connected with BA who have travelled on BA peak season dates (eg xmas to Cape Town for example) at very low rates. The whole family, whether they work for BA or not can also travel at low rates also and on guaranteed seats not standby.
And you can also throw in the fact that BA staff often get the upgrades to club class too (sometimes even first class), as long as they are dressed appropriately.
These perks are a massive loss. I BET Irvine offers an amnesty to the strikers next week. i.e. promise to return to work immediately and these these perks will be restored. Then we'll see what happens to the principals of the cabin crew!