Hi Paul,
The wiring is simple:
If you have a negative earth, the bulb will get the earth from the chassis, as it does now.
Another wire should go from the (+) positive pole of the battery, through a switch- to the 2nd filament of the bulb.
The switch is a “Pull switch”, which usually hangs on the chassis, with a spring to the break pole
(If this is the correct name for it) which is running from the pedal to the rear break lever.
(If you run a positive earth, all is the same, but the polarities are the other way round)
When you step on the break- the pole moves to the front, pulling the switch (Trough a spring) to close the circuit.
As to the rear lamp, you probably need to replace the bracket inside the housing to a double one and then fit a double filament bulb.
Here is a (Very) ugly sketch I just made.
Assume all of the "Earths" are grounded to the chassis, and therefore all
sorted to one another.
Hope it helps..
Good luck,
Noam.
email (option): noam10@gmail.com
Something like that.
MOT requirements should not be confused with legal ones.
An Mot cert only means the vehicle conforms to the requiremnts of the test at the time of the test.
It says so on the back of the old certificates.
No guarantee of roadworthiness or of legality.
The removal of the need for an MOT on older vehicles is a rivet counters dream.
[and thats not a critiscism of rivet counting]
Number plate should also be illuminated; WD fag-enders don't have the ability.
I got round it by having a separate stop tail set up on a detachable number plate, secured by wing nuts to a pannier frame.
Then when needing to appear as if I had counted enough rivets just removed the number plate.
If you have a fag end lamp beware that anything over 3 watts, even temporary, will melt the red lens.
email (option): deadsheds@yahoo.com
Hi Paul,
For simplicity have a look at this link
http://www.beckelektronika.nl/
The third section down, scroll to bottom item, there you go.
They are simplicity itself to wire up and incorporate the white light facing down for the number plate so you just need to drill a small window into the bottom of your housing.
They work brilliantly and the guy is wonderful to deal with, very helpful indeed.
I would highly recommend them, and I am not even on commission 
Darren
email (option): dwrudd@lineone.net
This LED bulb works much easier and is a straight fit to the tail light, it works on both + and - to earth. With an extra resistor fitted it works pretty good as both brake and tail light. You can find them on the for sale page of the website for 7,50 euro.
Henk
email (option): ahum@quicknet.nl
"for the number plate so you just need to drill a small window into the bottom of your housing."
not quite so simple, it must be illuminated so that it can be read at a certain distance and within a certain arc.
All these things I know having been, in my youth, educated in them by rivet counting policemen with time on their hands.
You name it I've been nicked for it.
I used to read the construction and use regs for a hobby, just to be able to argue in court, they are better than a bible for bullets to fire back,
my favourite
"Urinals in motor vehicles" and the regs around where and when to use them caused much consternation when I pointed out that a funnel in the floor was well out of order when used in spy vans.
email (option): deadsheds@yahoo.com