I went through the whole unpleasant gamut, 2 Warranty Managers (one of them useless, the other one brilliant), VW Technical (Rubbish), VW Customer Services (Mainly ineffective as they are tied up with VW Technical), VW Escalation team (Superb), 105 letters with letters to VW MD Chris Craft etc etc. Justice was done eventually but one has to be in for the long haul. 
Scary!

I’ve been to another dealer. The tech guy heard the noise straight after we drove off. Took the car inside the workshop and after 5 minutes the service advisor turned up saying: It’s normal. So I asked since what mileage they were supposed to sound like that. He said from 3000 miles. That’s strange because I’ve got 19000 on the clock and have noticed the noise only recently…
When asked if there is an official VW memo on that (like the wastegate rattle) he didn’t know. Or didn’t’ care, couldn't be bothered, you name it...
I don’t think it’s an engine problem but some weird resonance somewhere from the engine bay but without actually listening to another GTI I don’t want to waste time chasing VW. When a used GTI appears on the approved VW list somewhere around my area I’ll give it a go to find out.
I’ll record it somehow this week (if it’s not raining…) and maybe you guys can have a listen
