Left the bike on the charger overnight and try again this morning. Plenty of cranking but still no go.
Time to make use of that RAC membership. "Hmm," the RAC bloke says, " I reckon you've flooded it. I'll pull the fuse for the fuel pump to check that." We then had to work out how to remove the fairing panel and access the relay. Once decided that I had indeed flooded it by pumping petrol in the motor while the battery was struggling he says I'll get the plugs out and try and let it dry out. At which point he gives up when he realizes he doesn't have the 'right' socket.
Bike has now gone of to the local independent to be dried out and have new plugs fitted.

Lesson learnt always put the charger on when leaving the bike for any length of time.