UPDATE :
Pulled the engine today on a borrowed hoist.
Lifted up and wriggled just enough to get the old motor out and new one in.
All in all about 4 hours, some blood, lots of sweat, no tears.
Old stater is properly goosed.
New one turns the engine over well and the right way round which is a bonus.
I was kindly allowed hangar space as there were thunder storms today so I could work without getting wet.
Inspector counter signed engine going back in as I split the engine at the mounting frame to airframe. (5 bolts). 5th and last bolt was difficult to get back in but finally managed it.
Hoping to fly tomorrow.
Thanks for the advice
Martin