we're is the live wire to run the back lights on my Vauxhall Astra van 54 p?

I THINK you are asking something like: Where is the live wire so I can fix a new brake system, to make the back lights work when applying the brake pedal.

One has to wonder what is the problem with the brake lights you have at the moment. If they don't work it would be much better to sort that out, rather than butcher something together that will result in an MOT failure anyway.

XX
September 2015

Of course - if you make a connection between the brake lights and the rear lights - when you press the brake pedal the rear lights will come on - but in darkness when you turn the rear lights on the brake lights will also illuminate.

Bad luck...
September 2015

Will also run to the brake lights.
Easier to make a connection at the back of the car - a shorter wire-run.

Good Luck...
September 2015

Should be one down at your brake pedal at the switch

cdc
September 2015