"Throw out*bearings*(TOB) usually make*noise*when only when you press the clutch pedal. The reason for this is, it is the only time it is engaged and actually can make anoise. ... A*noise*from the*input shaft bearing*will raise and lower with engine speed, and not with vehicle speed."

Sounds like a bad ISB mate . People have driven 30,000k's with the noisy thing,so it shouldn't leave you stranded just real annoying.
Cheapest option is to pick up a working 2nd hand one as it's not an easy job to replace.
Swapping a gearbox is easy,it's just bolts.Youtube vids walk you through it. Grab a mate and a few beers