For almost a year now my car makes a whining/squeaking noise until I disengage the clutch (I looked on Youtube and it's exactly the same as people's "bad throwout bearing" videos).

It doesn't happen as soon as I start the car, but about 15-20 mins into the journey it starts.

Will it damage anything else on the car if I leave it until it fails completely (since people say with the labour required it's best to replace the entire clutch)?

I'm thinking about selling it/trading it in soon for a VW Polo, so I don't know whether to tell them what the problem is (and if it's a garage, they might knock a bit off the value, but less than it would cost me to fix it) or fix it, and hope it might add more onto the value (because it's being sold with a new clutch)?

How much will it cost to replace? The garage I'll use charged me £300 to replace the timing belt and head gasket

It's the 1.4 8v engine with only 30k miles on it. This car is the bane of my life.

If the bearing fails and collapses totally, then the damage involved could be catastrophic.
Imagine the bearing collapses at 5000 rpm, gets picked up by the flywheel, and scattered in every conceivable direction, very little in and around the flywheel would survive, including the gearbox and possibly the crank case.

If you trade the car in and tell them it has a noisy clutch release bearing, they will undoubtedly knock something off the value.
If you tell them that you've just spent about £300+ having a new clutch and bearing fitted, it will add no value to the vehicle as far as trade is concerned.

The bearing it's self will probably cost less than £20, however, getting to it involves removal of the gearbox which is labour intensive.
To replace the remainder of the clutch whilst the box is off, would really only put the cost up by about £80.00.

In total I'd estimate a clutch replacement to cost around £80 - £100 for the parts and about £250 for labour.

Depending on when you plan to trade depends whether or not it's worth spending £300+ having it fixed.
If the trade is imminent, then i wouldn't bother.
If you plan on keeping it a few years longer, then maybe i would.

Oh and welcome to the "Bane Club"

If the bearing has gone and you continue to drive eventually it will seize or break up which will undoubtedly do damage to the rest of the clutch at the very least you'll wreck the diaphragm spring which could leave you stranded, worst case it could damage the flywheel or bell housing

It's far better to get it fixed or if handy with spanners do it yourself it's more labour intensive than it is difficult, you'll struggle to sell it and it will only get worse.

As for vw polos well my brother is a specialist vw camper builder and next door to his workshop is a vw specialist garage and they are the first ones to tell you that vw reliability is a great myth which keeps them in business, just ask my work colleague who bought a brand new polo to have the turbo fail a year later then again at 2 years old replaced it with a passat which suffered a catastrophic engine failure 3 months after she bought it

VW Reliability isn't great at all. It's only because people assume they are and the allure of a VW badge that people get them.

Would be better serviced by a Fiesta 1.0 Eco Boost - great cars

Thanks guys, I don't think the next car purchase will happen soon enough for me to leave it unfortunately

The problem is, I always have at least one problem with my Punto. If I fix this, what's gonna break the week after

I've always heard good things about VWs from people I know that own one, and shocking things about Fiats. The problem is I don't like the look of many hatchbacks, except the GP (which is the main reason I bought it) and the 2010-onwards style Polo/Golf