If UK PLC was at war and the nation's survival depended on it then yes. Since it's not, the answer is no I would not accept a 5% pay cut.
On a personal level with kids and a mortgage it would hit me quite hard. But the main reason is that whilst 22/7M's intentions are admirable, the basic plan is crap.
I doubt it would save that much money in the grand scheme of things and it would just enhance the push factor when the economy eventually, but inevitably picks up. Furthermore, moral would go even further south than it is now.
Notwithstanding the problems with the UK's Social Security policy, the crux of the problem (as has been eluded to already) is the mismatch between the government's desire for us to be a world military power and the amount they're willing to spend.