Hi Ron,welcome to the forum.
The best place to help classic rover owners.
I would investigate further first before trusting the AA man!
How many miles had you done before it went wrong?
Did you check the levels before you started your journey?
Had it been off the road for a few years or used regular?
Check and top up your water and oil levels,then,if it starts ok but over heats within 5-10 mins,it could be a jammed shut thermostat causing it to overheat,blow off water pressure via the rad cap,thus an air lock stops heater working as its the high point of the cooling system!
Overheating can cause pinking,and oil pressure loss,had it happen to mine,"A 2000",I stopped quick,and it turned out to be a blocked thermostat,it had been sat unused for 17yrs,and the anti freeze had gone all cruddy,but once cleaned out,flushed through it was fine and now runs like a dream.
Is it a 2000/2200 or a V8??
Good luck and keep us up to date,and ask whatever Q's you need to,to sort it out.