B&S have solved this one for me. I emailed them the details above and within 2 hours they came back with a complete parts list with drawings and the part number for the electronic unit. I have now fitted this and it works great. Easy fit too just cut off all the old wires from the points, bolt it on, set the flywheel gap and away you go.
Full marks to B&S for standard of service.
Keith
April 2009