Hi, I'm going through the advisory notice on my most recent MOT for my 340 1.4 GL manual and i've got one of these:

"Front brakes only just met the fron brake imbalance requirements. It would appear that the braking system requires adjustment or repair. [3.7.A.2d]"

I've also got a "front to rear brake pipe corroded" as well as a few other minor things which I know how to fix. Here are my questions:

1) How do I adjust the front brake balance and how do I know when i've got it right?

2) Where can I buy brake pipes, are ones from a local motorfactors going to be ok?

There is no adjustment for front left/right balance. There is something wrong with your brakes;

partially seized calliper
Bent or seized slider pins (usually caused by knackered pin boots) (if one pad wearing more than other)
Air in one side (but normally you would have a spongy pedal awell)

Not an exhaustive list, I'd say the pins are the most likely, they allow the calliper to centre on the disk as there is only one piston.

Brakes pipes - yes get them made up (you will need the old one or its length) and change the rear flexi hose. May aswell do the axle brake pipe aswell.

Some places on the internet have lists of car applications and you can order up the exact length from their database.

It maybe worth your while getting a brake pipe kit to make your own, its not that hard if you do most of your own maintenance.