The BBS was a dealer option back in the day - they used to promote all types of aftermarket goodies from zender, bbs, kamei, votex etc etc as official accessories.
The body kit would've been fitted by a previous owner - unless in the unlikely event it was a gti that hung around the showroom when the kitted gtx appeared for the 1985 model year and the first buyer specified it this way. Very unlikely.
Check 'drivers found' website - it has all the brochures uploaded. GTIs came with a subtle check pattern in that period. http://www.driversfound.com/scirocco/history/uk/
Newton Commercial do replacement parcel shelves. http://www.newtoncomm.co.uk/cars/vw-gol ... board-kit/