If it is the bushes, and by the way it sounds like it might be, than don't let your Alfa dealer rip you off by fitting new ones. Some of the bushes on the back of the GTV are sold only with a set of new arms, so rip-off city here you come!
The best solution is Polyurethane bushes. Buy yourself a set of these from EB Spares and get them fitted by an Alfa specialist. Even if your bushes aren't knackered this is a worthwhile upgrade and you'll never need to change them again.
Be careful driving the car with knackered bushes though, you can cause serious damage to teh subframe doing just that, get them sorted ASAP! Good luck!
Where has he been?