Thanks for all your ideas,
This was flagged up to me by a colleague who is currently taking his MNR through the test at Beverley IVA station and was told a regular fog lamp switch fed from the switched lighting circuit was not sufficient.
The principle is to stop people leaving on their rear fogs whenever they put on their lights, which I think is fair enough, you often see people with fog lights still on the day after the fog has gone!
I think with Option 1 a latching relay will do the trick that is cleared by either switching off the lights or ignition. This will however need a push button (non latching) switch in the dash that must toggle the fog lights on/ off to get around the issue Simon mentions above.
Also Brumsters option of a modern switch unit that gives the mechanical interlocking will do the trick too.
Option 2 will allow a on/off style switch to be used but will require a bit more ingenuity due to the lack of doors, maybe if you have an alarm it could be fed from that, or maybe some appropriate diodes and a permanent 12V feed may be able to drive the buzzer when the switch is left on I will need to get out the multimeter to see if this would be feasible, I guess a double pole fog switch could be used, but most dash switches are only single pole.
Just another fun problem to solve!
Paul