Ive got the same on my mk1 sporting 1.6, id say by what you describe that your first motion shaft bearing has gone. Pretty straightforward to repair (according to my fiat mechanic mate) if you know what you doing!! Or look through your local yellow pages, and see if there any local gearbox specialists who could repair your current box for a reasonable price. If not then there of plenty of breakers out there who could supply you with a good 2nd hand box, although if you do that make sure they replace the seals on the driveshafts. (unlike the garage that did mine!) Otherwise they could be split and leak oil, then you bearings will be knackered and you will be trying to get gearbox number 3 like me! (Bad times) Hope it all goes good, an you get it sorted out.