Walsh hasn't lied about the cabin crew earnings, the figures are widely available and BA's figures tally with those available from the CAA. Just because you may not earn as much the stated average does not mean others do not. Mathematically others must exceed that average, and I know from first hand knowledge that £56K isn't too wide of the mark for a full time long haul CSD.
The question of volunteers replacing pilots is irrelevant. I doubt we'd like it, but then it couldn't be done. Nor would we base an entire campaign on the fact that we were irreplaceable and 'the only reason people fly BA' (as BASSA claimed) when it was painfully obvious that not only could we be replaced by people with 20 or fewer days training but people were quite happy to fly BA without us on board.