gti servo will fit but you might have to fit a rear brake compensator! this is the only real difference between 1.3/1.6 and 1.8 models, and 1.8s all got a compensator.
edit: not a dash out job, take the lower dash trim off and undo the 4 nuts behind the brake pedal, and the clip holding the pedal to the servo. Then go back to engine bay and undo 2 nuts holding master cylinder on, carefully pull it forward. Brake servo can then be removed & swapped, without cracking loose the master cylinder pipes and therefore without bleedign the brakes. I managed it on a RHD GTI so you should have no trouble
