Given the recent snow, check for loose parts underneath which may have been bashed and are rattling.

Yep, that was it, one of the two terminals on the milky green fuse nearest to the window was completely black, very odd, I sanded it off and with the help of the village octagenarian telling me which lights were working it appears that we have had a result. Many thanks again to the forum for the existing info resource and for the extra help today. 

56 minutes ago, MicMac said:

Given the recent snow, check for loose parts underneath which may have been bashed and are rattling.

Thanks MicMac, it's a bit awkward for me to get under the car for various reasons but I like the sound of your theory, the roads around here are very bad and we have been driving them in bad weather conditions so maybe an exhaust heat shield or similar has come adrift, it's fine when the car is moving, it's only really at idle or just off idle. I'm taking the car in on Wednesday for a check over, they're good lads there and probably won't charge me for an examination and a tighten up of any loose bits.