Is it possible to do a rear drum to disc convertion, or is it more hassle than its worth??? Can i buy the kits or would i have to get them off a HGT???

Yes it's more hassle than it's worth as the performance will be pretty much the same as it is with your drums. However to change to discs requires a few parts which can all be got from scrap yards of from Fiat parts dept.

Remember you can get parts from Marea 2.0 too which are easier to find in a scrap yard than a bravo HGT.