Re: beams
It's not the colour of the lamps that's at issue (although a lot of the older French cars had them, apparently on the basis that the yellowish light apparently 'pierces' thick fog better, rather than just bouncing back off it at the driver..?) The problem has more to do with the side of the road your car is designed to drive on.
On a standard Irish (RHD) car, each of the headlamp lenses has a panel that allows light to escape out and upwards towards the left-hand side of the road, so lighting up the ditch/hard shoulder. When you drive on the right-hand side of the road, of course, that results in you dazzling all the oncoming traffic (to your left) just as it passes you. Those little stick-on filters - if they're properly designed - don't just colour the light yellow, they have little rows of downward deflectors running across them which break up that sidewards beam.
In fact, you
could simply stick bits of insulating tape across those clear panels on the lenses (if you can reach them, i.e. if the whole lamp assembly isn't encased in a streamlined clear 'bubble') - this would achieve pretty much the same effect, but I think there may be some other law somewhere about not obscuring your lamps, even partially...
P.S. Yes, I forgot to mention that your
essence/gazole can be up to 10/15% cheaper from a supermarket filling station, as compared to on the motorway. Look out for Super-U or Hyper-U, if you're crossing Brittany - there's lots of them. (Incidentally, it goes without saying that a litre of mineral water or a packet of sweets/biscuits will also be marked up by about 200/300% in a motorway filling station!) There's also a massive Leclerc hypermarché just off the main road from Cherbourg to the ferryport - you'll recognise it from all the Irish and UK-reg cars filling up on wine before they take the boat home...