"Would limiting the length of the working day back to the 12.5 hour spreadover help to make the job more attractive? "
No. Not even close. Your average millennial balks at the thought of a 40hr working week, they’re sure as hell not going to want to do anywhere near a 12hr shift.
Personally I think over the next year or two the problem is going to solve itself. Come the end of next month the days of plentiful eastern europeans queuing up in their 10,000s to come here every year willing to work for peanuts, not just in lorry driving but in factory and warehouse work comes to an end. Lorry driver is never going to get Tier 2 status, DVLA have said multiple times that there’s plenty with licences to meet demand. So the lorry drivers who are already here on the stroke of midnight is the labour pool and it’s one that’s shrinking by thousands a year as people leave for greener pastures or just simply retire. The promise of a 15hr shift and automated vehicles in the next decade is going to put off many from coming into the job.
The savvy companies will work this out if they haven’t already and start improving terms - I remember being at Geopost, now DPD, when wage negotiations were ongoing as the WTD was coming in, PoA hadn’t yet been announced and the negotiations were looking at 25% wage rises to try to retain drivers by paying them the same for 4 days as they were getting for five. The far less savvy ones won’t until they can’t find anyone who’ll work for them, they phone the agency and say what they’re willing to pay and the agencies laugh down the phone at them before hanging up. Sure there’ll be the odd few who manage to find drivers who’ll work for peanuts but their wagons will be driven by people with DR10s and the like on their licences, the unemployable anywhere else.