I have not done this for decades and not on a P38, but what do i need to be able to do some brake lines? a flaring tool (which flare type do we need to use?), some cunifer (size?) some ends (thread/size?) a pipe bending spring one of those proper pipe bender things maybe ? All links/ recommendations welcome... thanks in advance

Rob

A flare tool that can do a double flare, something like this https://www.amazon.co.uk/Silverline-633545-Pipe-Flaring-9-Piece/dp/B000LFXPQ0/ref=sr_1_26 or https://www.amazon.co.uk/Double-Flaring-BOROCO-Degree-Automotive/dp/B0B56PCDXG/ref=sr_1_47, some standard brake pipe size 4.75mm or 3/16" Kunifer copper/nickel or copper pipe and some M10 fittings. If using Kunifer or copper, there's no need for a bending spring or pipe bender as it is soft enough to bend by hand.

The 2nd link that Richard put up is the one to get, it does a great job and is small enough to use in situ, its one of my favourite tools.
I don't know if all model years have them but my 2001 has two complicated looking curly pipes either side of the fuel tank which I made perfect replicas of using that tool and forming the tight bends round a suitable socket using my hands.

The other advantage with the second type is that they will do steel pipes far easier than the first type. I've got one of the first type, in fact I've got 3 for some reason, and when I wanted to replace just one end of a pipe on my son-in-law's Toyota, it really struggled to put a flare on a steel pipe. The pipe was plastic coated along its length except right at the end where it had rusted and ran the full length of the car so just cutting it and putting an inline join in was far easier than trying to feed a pipe along the full length, much like the ones that run over the fuel tank on a P38.