Ed B wrote:
Perhaps I'm just being a **** and the thing really should fit, but I
spent a good half hour last night trying to screw it on without cross
threading it. When screwed on as hard as possible it still squirts
everywhere, suggesting the plastic bit is too big for the tap I have.

PTFE tape wrapped round your tap screw thread thread before connecting
the hose screw top should take care of that. Works a treat.

Sarah