Thanks for all the help in this thread. I decided to follow the advice of some of the earlier suggestions here and settled on this:

https://www.ebay.co.uk/itm/112603916459

I am aware that you get what you pay for, but as I have mentioned, I do not ride at night but do ride frequently in Scotland. That means riding in wet, dull conditions often. So, my main requirement is to be seen rather than to illuminate the road ahead. So, I am hoping that this will satisfy my needs without a sizeable outlay and they are certainly better than my current set of lights.

Thanks to all who contributed.