Question for those that know:
In a protected strike, is the 12 week period from the strike ballot result, or from when the strikes are announced?
Or to phrase it another way - is the protected period (if the strike is protected) already running, and so by waiting, are they reducing the period they can actually strike for?
Taken to extreme (if this were the case) - call the strike after 28 days(4 weeks), and give the 1 week notice, means you reduce the protected period to 7 weeks. Is this the case? In which case, it isn't in the unions interest to wait, as they reduce the length and impact of any strike.
Of course if it is from the announcement of the strikes, then it makes sense to wait, as you disrupt BA bookings for 5 weeks + 12 weeks.