Do these make any difference to the car at all or is it best to just keep the £37?

I took.my.k&n off my old fabia vrs. Read that dust particals get through easier and nacker up the turbo. Just keep a normal paper filter clean and its just as good performance wise

Yeah the oil can knacker some MAFs etc

Had a Green cotton filter on mine for a year or so, it made no difference to performance or noise. I'd save the money and use an OEM filter.

Do these make any difference to the car?

None.

Funnily enough  I've had the same thought recently. I already have a pipercross panel in my tfsi. Its been in a couple of years but never been cleaned. I was thinking of going back to OE and selling the pipercross as I dont think its made any difference to noise or perfromance.