they are prity bad , is there any way of servo assesting them if so how ??

There actually alright once you do a few things to help:

(upgrade to vw1 calipers if yours is not 1984+)

new pagid pads/brembo discs

new flexi hoses

new brake fluid,well bled to make sure no air is in there

Adjust the rear shoes

with all this you can lock the wheels in the dry with a sudden flick of the foot when needed

just i was thinking of converting to a gt and a bit worried of the stoping power

change the brake fluid...

it may be possible to fit a servo...

personally id fit 15s and put my 280mm brakes on there as they would go straight on the polo and are for sale

This has been covered to death already - just note that there's no point fitting late MK2/MK2F calipers because G40 calipers are more common in scrap yards and take the same pads with the standard Polo solid discs. Its simply an option to use vented discs with them.

I'm running a GT without a servo and it doesnt have any trouble stopping. its just a case of pressing the brake pedal hard