Denzil,
Although you don't say what year your rangie is, I can only assume it's a P38 by your profile photo.
Anyway, if it is a P38 here goes:
Firstly, snap, exactly the same problem with my P38 DSE last MOT with a failure due to rear brake pipes rusty.
Now, here's your solution...
When they built the P38 they started with the Chassis and fitted fuel tank. With that they used steel pre-formed brake pipes, which fitted over the fuel tank. They then lowered the body onto the chassis and off it went.
However, you are now going to have to change these pipes and this is where you run into a problem.
If you try to buy the preformed pipes you will not be able to get them under the body, over the top of the fuel tank, under the bodywork, without ruining their preformed shape.
My independent garage came up with the solution and bought a reel of brass piping and 'fabricated' the brake pipes that way. Plus the beauty of using brass is that they won't rust again...!!
It's a long old process and could cost some serious money - it's the fitting that kills it, not the brass piping..
Hope this helps...
James.