As for UK Mk2 Golfs, then (at least) 4 sounds about right, although up to 1988 it was only ever Alan Minshaw's car(s) and very infrequently.
In rough order of appearance-
1984- Alan Minshaw/Demon Tweeks. Red car which appeared in a couple of rounds right at the end of the season
1985- Alan Minshaw/Demon Tweeks- same red car, only appeared at the Silverstone British GP meeting and the Tourist Trophy
1986- AFAIK no Golfs
1987 - Alan Minshaw/Demon Tweeks- about 4/5 rounds, although from photos I've seen, he used his Production Saloon Golf for at least some of them.
1988- 3 Golfs-
- Alan Minshaw bought an M3, but also ran his Golf for several different drivers- James Kaye, John Brindley, Andy Middlehurst, John Morris and Minshaw himself all appeared in the car at various points.
- Andrew Jeffrey/Specialist Cars Aberdeen
- James Shead/John Maguire Racing- these two cars were near-twins in corporate VW Motorsport white with blue stripes.
1989- 2 Golfs-
- Alan Minshaw/Demon Tweeks
- John Morris/Listers of Coventry. The Morris car got shunted very heavily late-season (Donington IIRC?) and I've got a very vague memory he may have used Minshaw's car for at least one race after that.