Having a grounded metal case on a PC probably helps meet RFI/EMI emission requirements.
Not sure about the UK, but the metal case on every VCR I have looked at is connected to "circuit common". Most units have a 2-wire cord, with the neutral side of the line connected to circuit common through a typical 3.3 megohm resistance (for static discharge). The shells of the I/O connectors are also connected to the common bus, and to earth ground through the shield on the coaxial antenna input cable.
