well I'm home having covered about 350 miles this weekend. The optimate was still showing 'charging' yesterday morning but there was enough juice to start the bike so decided to chance it. Stopped for fuel 95 miles later and plenty of juice...then it was left (outdoors, poor thing!) overnight and I checked it at 9am this morning...still plenty of juice! So scenic 200 mile journey back today, with 3 stops, and still the battery seems fine. Going to leave it a few days now and see what happens...

very weird!