Courtesy call almost within a couple of hours to say the fault was confirmed and work authorised by [Lexus] Warranty. Part ordered and should be in tomorrow; car should be back then.
All in all, a very positive experience. Usual top quality Lexus service from MK
...although have to say not only was the dealership totally deserted but it did look like there were minimum number of staff on hand: Receptionist, Service Adviser, One Salesman and a couple of managers in their offices.