Your local car parts shop should have rolls of 3/16” copper pipe and bags of male and female unions (10mm nut) to fit. Two rolls and a bag of each should do the whole car, but there are a couple of unions on the ABS unit that you’ll have to re-use.
Generic brake pipe flare tools (3/16”) are all over Amazon, about £25.
Do look up and study OP1 and OP2 flares, and don’t be tempted to make a female flare by just opening up the end of the pipe in a single layer. A good look at the original fitting should tell you whether to do OP1 or 2. Practice, and use a dab of red rubber grease to ease the flaring. At least once, you’ll produce a beautiful flare and found you’ve forgotten to put the union on first.
Before you start, open a bleed nipple somewhere and wedge the brake pedal down - this will stop the system draining out once it’s open. Also, chop the old pipe out with wire cutters in sections and follow it with the copper, which can be run like electrical wiring. This way, you’ll get the routing correct.
When you’re done, don’t go pumping the pedal to bleed all that air through - fill the reservoir, open the bleed nipples, and go for a quick cuppa. Once they’re all dripping, tighten up and pedal bleed as normal.
Rusty pipes are a common problem up here, and I’ve done several of my own and my mates’ cars. Good luck, and let us know how you get on.
Oh, and remember that copper pipes don’t need tightening like steel ones - snug up by hand and maybe half a turn. Test the system well before you drive the car, engine running and a good hard press on the pedal. Any drippers - another 1/4 turn. If you overtighten them, they’ll just fly apart under pressure.
