I go to France regularly in my Discovery - it's a good vehicle for what you have in mind as the slightly higher driving position will give you a good all round view and it makes things a little easier when you're uncertain of quite how to do this turn or how this junction works.

Others have covered stuff about documents etc so no need to repeat it but below are a few points that might catch you out, at least initially.

It may seem obvious that you'll have to drive on the right but it means that all the road positioning skills and things like that which are second nature in the UK essentially have to be done backwards in France and that can require a bit of concentration until you get the hang of it. For me now I can flip from one system to the other pretty much automatically but it did take a few trips before that was the case and until that happened I had a "give way to everybody", just in case I'd got it wrong approach.

The other main problem with UK cars in France is that the driver is on the kerb side and that causes visibility problems when you want to overtake. OK, you're not going to be overtaking a huge amount in a Discovery but sooner or later you'll be stuck behind a truck or a tractor and unable to see what's coming as you can't pull out far enough. There's no answer to that other than safety first (unless you absolutely trust whoever is in the front passenger seat to act as your eyes), even if it does mean annoying the long queue of locals behind you who can see if the road is clear.

My other piece of advice would be to steer clear of Paris, at least until you're happy with driving in France. Like London, Parisian motorists don't take prisoners and trying to cope with the volume and density of traffic while being uncertain about where you're going (even with sat-nav) and uncertain about "reverse" driving doesn't sound like a holiday to me. Paris is a fabulous city and well worth a visit but find somewhere just outside and come in on the train. Your blood pressure will thank you!