We will also be going on MoT to France.
The first question is whether or not your car is positive or negative earth? If it is still positive earth, as mine is, then this makes installing electrical equipment more difficult.
Assuming your car has been converted to negative earth then there are lots of charger sockets you could fit. You can either fit a cigarette lighter type socket and then use one of the chargers that plugs into where the cigarette lighter would go or fit a dedicated charger. To my mind there is no point fitting the cigarette lighter type these days as hardly anybody smokes any more!
With positive earth the socket must be completely electrically isolated from the body of the car and that is entirely possible but there is still the risk of the charging cable metal end touching the car body and if it does it needs to blow a fuse rather than cause a fire......
I decided that it was all too much trouble with a positive earth car and also it being a tourer with very limited space under the dashboard so I have one of those external battery "bricks" that can charge the iPhone several times over.
12voltplanet.co.uk have a selection of charging sockets some of which are weatherproof with discreet covers over the charging ports. You will need to decide whether you want the socket to be always live or live only with the ignition on. Then you need to fit an appropriate in-line fuse that you can access if you need to change the fuse.
Have a look here:
https://www.12voltplanet.co.uk/in-vehicle-power.html They also sell a wiring kit that already has an in-line fuse fitted.
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
Stephen