Found this on another site might be of help.... Alot of reading tho

To improve the braking on the MK1 Golf GTI many people including myself have used other VW parts to get braking how it should be.
This can be a very cheap mod to do if you get lucky in the scrap yards and really should cost you no more than ?150 by the end of it.
There are other companies out there that do larger brake conversions, you only need these if you have serious power and using it on track, for most road/engine applications the 256mm up grade is suitable.
The parts you will need are
256mm discs in the four stud pattern, Late MK2 golf 16v lends itself to this
Calipers from a Late MK2 16v and you might as well get some decent pads while your here, choice is yours but i have run pagid and found them to be fine.
Carriers ( you will need these to hold and space the calipers, you can't run the 16v calipers on the standard set up) you can get these from early Audi coupes, if your in a breakers check that the audi has the same handles as your golf, if it does it will fit as a general rule of thumb. But make sure it has the larger discs!
Audi 80 quattro (83 to 85)
Audi 90 5-cylinder (85 to 87)
Audi Coupe 5-cylinder (85 to 88)
Part Numbers:
Caliper carriers - 853 615 125
Carrier bolts - N900 689 02
Sliding pin bolts - 321 615 141
you can also use the very rare 16v scirocco items too if you can find one......
Now you could leave it there but you might as well go the whole hog.
Get the Larger master cylinder ( 22.5mm ) and 9 inch servo from the 16v or a passat.
This bolts more or less into place, you may need to space the Servo out a bit more on the bracket than the original mk1 item, a few washers/around 4mm will be fine.
You will also need to T peice the brake lines, this is no big issue.
This set up gives you more bite from the disc and pads and better pedal travel.
Braided brake lines are also a bonus if you can spend the ?40 for the set up, they are not needed but will help improve the braking futher.
If you fancy going larger i have been given the following advice to run 280mm fronts,
all used parts except for disks and pads,and bottom ball joints, the list is:
corrado 16v front hubs modify the strut top hole to allow correct camber bolt to fit.
remove steel spacer sleev from hub mount bracket
mk111 gti calipers and carriers (mk3 non gti are same caliper but thinner, different pads)
mk11 gti track rods
mk11 16v bottom ball joint, re drill the centre hole to suit mk1 arm.
>mk11 g6o disks
mk111 gti pads