I was looking for a source of air filters and about to buy from: https://runautoparts.com.au/filters-servicing.html who have a nice assortment, when I came across K&N. https://www.knfilters.com/search/product.aspx?prod=33-2865 They are expensive and make a lot of claims but what they say seems to make sense.

 

Has anyone fitted these? If so, are they worth it?

I have used K&N panel filters on a number of cars, in fact my VRS came with one fitted by the previous owner. If you are expecting any performance gains with these filters, you will be disappointed. If on the other hand you want a filter for life that only needs cleaning ever 50k miles, this is the filter for you. Mind you, I clean mine every 30k, don't like to leave it too long before a clean. 

and you have to re-oil and if you overdo it it can foul up the air sensor  MAF  I used one for years on a Terrano  it was fine but have never bought another for other cars

K&N (and similar filters) flow best when filtering the least (and yes, I have used them in the past).  And, as Cheshire cat says, the oil can contaminate the MAF.

 

You are better off using a good paper filter and changing at half the factory interval.  The VW inlet is a reasonably efficient design.