Thanks to Ned and James at Autolusso, there's a kit of parts en route to my mechanic (for a very reasonable price) :-)
I found out a couple of months ago (at around 68K) that the belt *hadn't* been changed at the 72K service (carried out at 54K)... I was somewhat slack in booking the ol' girl in for the work and so, at 73,386 miles she gave up.
If there's one thing I've learned, it's never take a service book at face value... And avoid costly work by getting stuff done sooner. OK, if there's *two* things I've learned...
...nobody expects the Spanish Inquisition ;-)