I know this doesn't help you Mathew, but for information a bias brake set up which allows you to keep the standard pedal and servo is available from Demon Tweeks, but it ain't cheap at £346 +VAT and then you still need master cylinders at about £70+.
Do you really need to change all the pedals anyway for a full pedal box, wouldn't it be possible to modify the existing brake pedal arrangement to actuate the balance bar? (Just to be clear though, I've never taken the pedal or servo etc off my mk3 or any Polo, and I've not even seen a mk1 up close).
And to top off any balance bar arrangement you really need the remote dash mounted adjustment knob and cable. These are also expensive, at about £70 quid up, and for my kit car I had to spend nearly £90 on a little right angle adapter so the cable is clear of the other pedals. What's the point having adjustable braking if you can't change it whilst on the move?