Hi, Yes I did check and re-check the kill switch.
Managed to resolve it in the end with some advice from a fellow boat owner at the boat yard.
First off, the suggestion was I could have totally flooded the engine.
I had established i was getting a spark by trying the plugs against the engine block.
So removed all spark plugs and just turned the engine over a few times again and then left the plugs out for 10 minutes to let the excess fuel evaporate.
I replaced the plugs and tried again, nothing, just kept turning over and not attempting to fire up.
Was just giving up and putting the cowling cover back on when I noticed the manual choke knob on the casing; I had previously only used the key push operated choke; so I pulled that out, pushed it in, pulled it out again.
Turned the key and there has a hint of an attempt to fire up.
Turned the key again and it was biting but not firing.
Third turn of the key and it bubbled into life !
Bingo, water pumping, engine idling happily.
Left it for a few minutes idling.
Key off, key on, instant fire up and ticking over nicely.
All sweet and happiness again !
Lesson learned on flooding engine and how to deal with it.