Thanks for the replies everyone, really appreciate it. After the almost-failed-to-start episode last Sunday I've left the bike off charger expecting it to be dead, but last night she turned over no problems at all. Most peculiar. I'll give her a good shakedown ride this weekend and will keep the bike trailer on standby just in case, though part of me thinks that at seven years old the battery probably wants replacing anyway, especially if I ever plan to take her across again on the ferry.
With that, thanks for all the feedback and recommendations. ����
If have alarm on bike must disable on ferry save battery and problem noise, also tracker will feel ferry move so will drain battery also