So we've booked a road trip to the Alps 6th January and I have one concern that the battery runs flat with the FF being parked in the cold for the majority of a week and we won't be able to get in with the dodgy driver's door lock.

At the moment there is a crappy bit of brown wire to the +ve that the FF can be jumped off of to open the door.

As a precaution I was thinking of running a 35mm battery lead from the +ve terminal to tucked somewhere under the front grill with an insulated cap over the end, then in an emergency locked-out situation someone can just hook jump leads on and we can get it

1 do I need one that big (35mm) to get some charge to open the door?

2 Is this a sensible/best option (I thought about an Anderson but then the average person with a set of jump leads won't have an Anderson connector)

3 Any other suggestions (obvious one replace the door lock! )

Do you have a tow bar and the two sockets?

No I don't have a towbar, maybe in a year or tow

two**

Ditto: On mine ,"Pin 4" on the White (12S) towbar socket is permanently live.

Sounds like we need to get a towbar!

An Andersen might be a good call, then make up an Andersen to jump lead setup to keep in the tool kit. That way you're not relying on someone else having jump leads.

Going back to your first post.

1 No you don’t need 35mm² cable, 4mm² would be more than adequate and robust enough not to get damaged.
You could connect a red cable to the +ve jump post and a black cable to the -ve jump post and run both cables to behind the front grille. I’d be inclined to terminate each cable in plastic cable connector to ensure nothing untoward happens. No doubt you can figure out how you intend to connect to the cables when needed.
To be absolutely sure about protection for the red cable I’d be inclined to install an in-line fuse holder in it near to the jump post with a 20A fuse in it.

2 The above is probably you best bet in the circumstances.

3 Without doubt I’d sort your door lock problem. Urgent imo.

As above get yourself a set of jump leads, just don’t leave them in the car.

Just to clarify, my suggestion of using 4mm² cables is to allow you to connect a battery charger or to another car battery to allow you to open your drivers door not to start the engine. Once you get into the car you can open the bonnet and connect onto the jump posts directly with jump leads to start the engine.

I actually fixed the key lock - took about two years + five minutes to do the job The column wasn't aligned with the locking mechanism

Thank you nicedayfor it will do that. I have some inline fuses too