How fast could BA recruit/train/roster replacement CC?
There are a notable number of cabin crew, who were on temporary contracts, fairly recently let go by BA, who could be re-employed pretty quickly. There are also others, waiting in the wings, having been placed in a holding pool but told (so far) that there are currently no jobs available. What exact numbers are involved in these 2 groups, I couldn't say.
Then you have the Virgin/BMI/Flyglobespan cabin crew (300?) all made redundant in recent months. From scratch it doesn't take much time (2 weeks-ish) to train cabin crew though you might have a further wait if any additional security clearnces are sought. In any event, I think BA could get at least 500 cabin crew up and running in a few weeks, with a substantial number of them having already being qualified by BA or other airlines.
It's been noted on this thread that CC tend to go sick when they don't fancy a sector
That is
fact. It is a common ploy, openly heard being discussed amongst cabin crew talking on the bus, around a hotel pool, or even in the crew report centre. Seriously work-shy, some of them.