In these situations companies can and do sack strikers- that's why there's the limited compensation route (after a usually very delayed tribunal).
Willy would only have to sack a handful before the rest come back to work on new Ts & Cs.....obviously the ones he chooses to fire will never work for BA again and if you were hiring (and who is in this climate?) you'd be forgiven for overlooking someone sacked for partaking in/organising non-goal orientated strike action that followed non-negotiation and non-compromise.
I would imagine that anyone threatening the business in such a way can expect the nicely-nicely BA that we all take for granted to give way to gloves-off, survival mode BA, where Willy will do whatever it takes to get the airline running smoothly again, even if that means paying some small fines to weed out the trouble makers and show the public that he has no other option now his hand has been forced....lots to think about