Warning triangles are no longer obligatory, a spare bulb set is. If you wear glasses you're supposed to carry a spare pair, but I don't.
If you have the new Euro plates, then you won't need the GB as it's built in, otherwise yes.
I wouldn't bother with beam deflectors if you're only here for the weekend. You won't be doing any driving at night here - Friday, ribs and booze, Saturday Barby and Booze. See? I've just saved you 10 quid (we drove here for 5 years without deflectors).
Green cards are the standard form of insurance policy in Europe. It's a good idea to have a GC extension to your UK policy as it extends your cover in Europe to match what it is in the UK, otherwise your cover becomes third party liability cover only when you get off the boat. If your car gets stolen, you'd be in trouble. A valid insurance policy is obligatory: you have to carry your car registration papers (V5? I forget now) and your insurance policy (not just the cover note/certificate!!!) with you while driving the vehicle. An international accident form is sensible in case the worst happens. You also need to have your driving license.
You need your passport only to get back into the UK, not while you are out here. However, you need some form of personal identification on you.
I'd advise you get an E111 emergency health costs cover certificate from the post office: you might also want to get breakdown cover. However, if you broke down, you could ring me I'd come out and get you - we have a tow hook
.
While driving from the port at the Hoek, you need to be ready to give way to the right at minor junctions - just be ready to stop at all times. If you would like road rules/driving advice, post again and I'll try and write a little summary.
You get free condoms with your meal at the Restaurant we are going to