I need to replace 13 pin socket with fog cut out. I have had a look on line but there are so many poor Chinese fakes. Anyone suggest a good make or source. The original was made in Germany.
In many (most?) cases with ECU updating for towing, the rear fog lights on the towing vehicle <should> automatically cut out but leave those on the trailer working. You will need to check it yourself. It is not an offence in the UK (AFAIK) to have both tow and trailer rear fogs working simultaneously.
If the original socket was German it was likely by Hella - which is a good place to start.
I agree with Woodentop, most modern vehicle will sense a trailer / caravan is attached and sort the rear fog out , if this is some earlier system it would have require some adaptation to the towing vehicle wiring? as a break will be required? You could simply add a relay to switch the fog lamps off when towing?