Great news today.
I finally got over to the Slingshot today, to check out the modification that I'd made to the earthing strap, on the battery.
Due to bad health it had taken, almost 2 months, to get this done and try turning the engine over.
Everything worked fine. The engine sprung strait into action after more than a year sitting, doing absolutely, nothing.... it sounded just so, so sweet.
My next job is to reconnect one of the angel-eyes (that has a broken lead, running to it). Then it will require, its yearly testing for road worthiness (known in the UK as an "MOT Test." https://www.gov.uk/getting-an-mot/the-mot-test ).
Assuming that all goes well, with the test, then my wife and I may get to enjoy the use of it, this year.
So one little step forward today, but a masive leap towards rideing again.