Back from Fords - £72 lighter in pocket - they have confirmed that both sensors heating elements are shorted to ground. They want another couple of hours to check the ecu and wiring - if ecu then it's easy but expensive, if wiring they have said they will sort and charge the 2 hour fee. Helpfully they also included a health check which according to their price I need a further £1400 of work - tyre, shock absorbers, discs etc. I'll get a second opinion on this.......