I used to work in a VW dealership from 84 onwards and all new mk2s and other VWs and Audis that I PDI'd were supplied to us from VW/Audi didn't come with any radios just a blanking piece fitted where the radio would normally be.
Over the years we fitted as a 'dealer fit' Blaupunkt, Panasonic, Pioneer, Sony which needed fitting kits/surrounds that matched the shape of the mk2 dash properly. ( some dealers didn't bother and The fitment looked cr@p

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When I questioned this I was told by one of the salesmen that it was because *VW UK didn't want to pay VW/Audi Germany's prices for Radios*.
VW's and Audi's that came from Europe and not via the UK VW/Audi dealerships seemed to have factory fitted radios as they were different spec and matched the dashes better.
* this is what I was told at the time but it may not be true

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