It is unsurprising they have immediately had to resort to DEC's. The offer will be unappealing to most currently employed pilots given the rostering/pay/freeze issues.
The more interesting question is whether they will get enough external applicants, given that you must now have the right to live and work in the UK on top of being a currently operating captain with A320 experience (does this mean you have to be currently operating the A320 as a captain? There is your example of ambiguity for when they ask you at selection - you're welcome). Oh and as skyrocket says, you get a 6 year freeze at Gatwick. I would suggest the group of people who meet all these requirements and can be enticed by the current offer will not be large. Smaller still once the recruitment process has taken its toll.