Phillipo,
Millers Commercials fitting the new starter motor today, plus service. Had the car sent on a transporter and Millers have sent me images of the work. Process exactly as Cerialsurfer has described, replacement of starter motor done on service and accessed from beneath. Andrew r had the same fix last year and seems to be the best solution.
image shows new starter in place, viewed from beneath with trays removed.

The general scene, with my car naked
