Please reassure me that this is normal. Whilst driving with the windows down on my 75k petrol mk 1 vrs I noticed a faint whistling not screeching sound from the turbo when I put my foot down cannot hear it with windows shut.car has full dealer history run on edge sport oil noise gets slightly louder as revs increase performance is normal please don't laugh as its my first turbo car

Sounds normal enough. At low speeds u should hear the turbo with the windows shut, but at 80 not so much.

Should make a "whooshing" noise from about 2000rpm and go quieter above 4000rpm

Should be a whistling indeed! If its really loud and you've not got a big air filter then there's a chance of a boost leak. More often than not it's just normal noise!