So much knowledgeable and valuable advice in such a short time - many thanks to all.
Once the rain stops here, I'll take a closer look at the fuse box in the daylight and hopefully actually locate the battery. Then I have someone coming over later with the necessary electrical gubbins to check whether the battery is dead or whether there's another problem. It's a 2012 model, so the battery may well have been original and well past it's sell-by date.
Thanks again for all the sage advice. I may be a mechanical novice, but the support network is excellent.
