VIN seems to check out ok:
The VIN code WFOEXXGBBEGR93603 breaks down as
Manufacturer Identifier: Ford Werke A.G. (Germany)
Body type: 3 Door Hatchback
Line: Ford Germany (Own Assembly)
Assembly Plant: Genk (Belgium)
Model: Mondeo/Cougar/Sierra/Cortina/Taunus
Year: 1986 (some codes are used for more than one year)
Month: October
Production Sequence: 83603
Seats have been partly retrimmed in leather by the looks of it, probably because the material on the bolsters was worn.
RS500 front bar, splitter, rear spoiler, strut braces and a few engine bay mods, but I think it's a genuine RS Cosworth.