Before you leave:

Make sure timing/cambelt is not nearing the end of it's life.  If you have no service history look for a sticker in engine compartment that indicates when it was last changed.  If you don't know when it was last changed, a full service with replacement of all belts might cost 300 quid, but well worth it.

Check the exhaust isn't about to break/fall off.  The cost of front section of exhaust for a van in France is over 400 Euros.

It is a legal requirement in France not to mix tyre brands on the same axle.  The French police don't seem to check for this because I have been stopped a few times with 4 different brands of tyre on the van but if you get a puncture then some tyre companies will not sell you a single tyre, they will make you replace both tyres on the axle if they don't have a matching tyre.  For this reason it is good idea to spend a bit extra and get Michelin tyres because you will always be able to find a matching Michelin tyre in France.

The cost of replacement parts in Europe is considerably more expensive than the UK, and availability of second hand parts is limited.  A neConsider taking the following spares alternator or started motor can set you back over 500 euros, and both items can be picked up second hand on ebay for less than 30 quid each.   Even if you don't feel confident to change these items yourself you can always get a local mechanic to fit them for you and make big savings.

Old camper van recommended things to take.

• Alternator
• Starter motor
• Throttle and clutch cables
• Spare bulbs for all lights (it's a legal requirement to carry a spare bulb set in some European countries)
• Jump leads
• Spanners/sockets/extension bar to change starter motor or alternator.
• Warning triangle and high visibility vests for all passengers (a legal requirement in France, you can buy much cheaper in the first supermarket you come to in France than you can on the Ferry)