Sid Hayers made a few films that could be classed as British Gialli. Certainly the one that fits the bill the most, I would say, is his film 'Deadly Strangers' (1974) starring Hayley Mills, Simon Ward and Sterling Hayden. It's a great little film and often overlooked, has a very twisty plot and to be honest it had me stumped, as regards working out who the murderer was, pretty much right up to the finale.
I don't think it ever had a UK VHS release, my copy is from an American tape.