I don't support the strike when they are asking for 15%, it's ridiculous.
Those who have been interviewed have always highlighted the overwork, and lack of nursing staff, both huge issues I agree. However, neither of those is down to pay. Most of the grievances are down to other issues. Equally important, and mostly down to the lack of staff. I think it is simplistic to say though, that more pay will lead to staff retention. I suspect if they get a good pay rise, many will go part-time, to mitigate the stress of work. More pay also means there is less to go round for new hires, so it is a vicious circle.
A point many are missing too, is though it is more expensive to hire agency nurses on an hourly rate, it is still less expensive than having an employee. The NHS saves money as they don't have to pay holiday pay, or sick pay, or National Insurance or pension payments. Another catch 22.