PipH

I think you may need one of these or equivalent to fix it. https://www.darksidedevelopments.co.uk/products/ppd170-used-bkd-aluminium-inlet-manifold-conversion-kit.html Seems like it is another common failing.

" Something else to note is that there was a number of people who reported an issue with one brand of clutch, where the release mechanism could fail in such a way that it would still work, but slowly that eat away and the housing from the inside if it occurred. " I think this is the post referred to. I think it only applies to the 2l diesel. If the noise is your gearbox being slowly eaten, then the cost will be much more if left. If VW take the clutch apart & find the gearbox damaged, they should pay for the repairs.

Has it had the emissions update by VW. If not, get it booked in & clear the fault before leaving it with them. It then has 2 years warranty for " Trust Building Measures " that includes the EGR & other expensive items. https://www.skoda.co.uk/owners/ea189

May be one of these would do the trick for you. https://www.ebay.co.uk/itm/Hot-Diesel-Start-Starting-Fix-VW-Golf-Passat-Audi-Seat-Skoda-1-9-2-0-2-5-TDI/201911548894?epid=0&hash=item2f02ddbbde:g:Ry0AAOSw0vBUgZKs