Apparently it was the rear driveshafts/halfshafts. They replaced them, did a full wash and valet and basic safety check inc pads/tyres/lights etc and gave it back with an extra £15 fuel and a bottle of champagne. Cant complain!
Had a drive of a newish Yaris 1 litre as the courtesy car. Seemed plenty for a run-around car. Quite a bit of transmission and road noise but plenty of grunt and sipped fuel. Couple of issues with it:
Being 6'1 I couldn't get the rear seat headrests high enough to not jab me between the shoulder blades while sat in the rear, even at max height- felt like i had to lean forward all the time. You cant see the end of the bonnet (or any of it to be honest) - making it fairly hard to judge where the end of the car is while slow maneuvering. Being a passenger part of the time i found the digital magnified dash a little annoying - I couldnt watch it easily and from the passenger seat it wobbled around a lot. Obviously not critical but I'd rather have it blank than half-visible and wobbling!
J