There is such a large amount of movement in the whole aviation industry at the moment, it's hardly surprising that FI's are thin on the ground.
People straight out of training are easy to find, but anyone with any experience and especially those with IR and aero's experience are like gold dust.
Can we solve this problem by allowing PPL's to instruct? To a certain extent, but we must be careful not to get to old problem of having people instruct for free. If the CAA were to allow all holder's of FI ratings to be paid, then go for it.
Otherwise, the industry will just have wake up and smell the coffee and people will just have to accept that an FI will cost alot more. Hopefully the days of £10/flying hour will soon be long gone. (They certainly are in my club, but I'm not so sure about others.)