If the pipe(s) are badly rusted, no amount of "Camouflage" or tarting up is going to cure them. From a safety point of view, because the rust has already penetrated into the steel, just replace them with copper/cupro nickel piping....cheap as chips.
I have not had time to look at them yet since it passed the mot due to work, but will in the next few days. Depending how bad they are I will formulate a plan.
What sort of price would I be looking at to replace the pipes with copper?
TD4 2006.