Is it worse when first started or when it has been running for a while (I know you mentioned noisy when cold - not sure if this was cold weather or first started).
If it is not worse when very hot then probably not big ends etc.. Could be piston slap but my gut feel would be the hydraulic tappets.
I had a VW engine a few years ago with a dodgy hydraulic tappet, using an engine flush helped but eventually I replaced them . If you do think it is this change the water pump, antifreeze and fit new cambelt kit whilst you are at it - if I remember correctly it wasn't tooo difficult - but it was a loooong time ago.
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