I have seen one Anthracite CSi in the UK. I recall it being a later car (1975) and am pretty sure it was the original colour. The interior was red leather and it was a really nice colour combination.
It belonged to a guy called Nick Brown, from the Stirling area of Scotland. Nick and I met after he was Coupe spotting in the car park of a VW show my wife and I went to in the grounds of the Doune motor museum about 1993. He saw my CSi and left a note on the windscreen.
Last I heard Nick was away working in London, then possibly USA.
Dont know if the car was taken down to London.