Yes Erik, you can buy them on the ferry but in all honesty I never change the lamps on my TF (although I can change just by moving the lever). I have never bothered with this since the French stopped using yellow lamps in the 70's

All the roads you will drive on will be lit, you will not drive on country roads (unless you get badly lost

).
OK, the plan

:
If you arrive early at Dover (ferry especially Norfolk Lines are cheaper than the train) you can travel up the M20 to the M25 following Dartford and drive to the hotel (I will list the ones I like the look of soon, you have the prices on an earlier thread). Here you will go through your first tunnel under the river Thames, take the left side tunnel, there are two lanes through two tunnels and stay on the left, it will be easier to get to your hotel this way, you will need £1.50p in cash to go through the tolls. At the hotel ask if you can check in early, if not tell them you are here as you will not be back until midnight, then you can go shopping as the massive shopping complex of Lakeside is 1km away.
Dawn and I will meet you at the hotel at 17.30 and take you to the start at Wimbledon in south west London, please arrive hungry as the owner of the American themed diner will donate at least 10% directly to the charity and the food is good too.
The police will set us on our way from 20.00 and the Roadbook will be in km's for you. In the book you will find out about the route and what you will see on the way, read it early as you will not have much time when you are driving, the navigator will be working hard I can tell you. You will cross the River many times including opening bridges, a wooden bridge, a counter balance bridge and tunnels some of which date back to Brunel from the 19th century. You will drive through the London Docklands pass pubs that are 500 years old, parts of the London you will see are over 1,000 years old. In the Canary Wharf area you will pass through security checks where your car will be swabbed for traces of explosives, if you are unwilling to go through here please let me know and I will give you an alternative route.
Many Bus Lanes finish at 19.00 so we should not suffer too much traffic, I have created a good route that I'm sure you will enjoy.
I will ensure you have an English car with you all the way, we will travel in groups of three maximum as stopping for pictures will be difficult in larger numbers.
We will stop in Greenwich for coffee and supper where some will go home, we will continue the whole route of the River passing under the QE11 bridge and back to your hotel.
In the morning after breakfast you can do more shopping as Lakeside opens at 10.00, you are one hour away from Dover at this point so getting home at a good time is possible.
Don't forget we are one hour behind you so set your clocks back one hour when you arrive.
There will be a commemorative plaque for the event for the early bookings only and, I think we will create a special for THE DAY.
Anything else, just ask.