Thanks for all the replies....
sadly the ones Stu has are from older Optis, as is the spares engine on ebay, similarly the link Brad posted for Boatmad...
These are all the 'united technologies' type with the 9 toothed dog gear, which marine engineers and american marine both have in stock....
The type we have is the later Delko type with the solenoid alongside and 14 teeth on the cog...
Have taken it over to a specialist in Haverfordwest and will see what they can do....awaiting their call back...
Any more suggestions still appreciated....
Dan