Just a quick update and thanks for the replies. Got the car back tonight. All seems well now. Apparently there was air in the system which lodged at one of the rear callipers and caused it to stick open. Also caused the rest of the system to be very soft. Lots of "we're very sorry" from the dealership, a tank of diesel and the promise of money off the 1st service. The service manager is contacting Toyota for more info and I'll be interested to hear their explanation. Will update further if there's anything worth posting.