Thank you for the info, Bill.
I have read the thread and found a few others which are relevant but sadly, it seems, none quite fit my xenon fitted S320. If there is a small lever on my set-up then I can't find it unless it is a major engineering task to get at it.
It seems a bit odd that it should need a dealer to make the switch, unless there is a dealer stationed at Dover/Calais and on 24 hour call, as otherwise one is bound to fall foul of the law on one side of the channel or the other. Odd also that such a basic need gets no mention in the car's manual.
I do not plan to drive after dark on my trip so I guess I shall just have to hope I am not pulled over for a random check.
Once again Bill, thanks for your input. This sure is an amazingly interesting site to browse.
Chhers, Gerry