Thank you all for your input, checked everything and A OK. So, out came old faithful ..... WD40 and hey ho, a blast of that up its trunk and around the terminals and it was back too its noisy else.
Mine packed up during a ride back from London in a monsoon. I only found out that it wasn't working when I tried to use it in anger and all got was a pathetic buzz. When it dried out it started working again.