Bear in mind the Golf's rear track is much narrower than the front's for typical hot hatch handling characteristics. Start mucking about with spacers for 'stance' and aesthetics and the scrub radius and handling suffer.
If you do want to push the back out more, consider Scirocco alloy hubs for unsprung mass reduction and +15mm per side more track, then balance it with 10mm spacers at the front to maintain a wider front track. You'll need to camber in the front the wheels to avoid arch fouling though, plus removing the middle arch liner screw/mount. +15-20mm at the back will likely catch the arches if you load the car enough, or drive it hard enough, but for physical confirmation before driving it, remove the springs and dampers and jack the wheels up as far as they'll go into the arch to check the clearance.
