jg

I don't think such a thing actually exists.

You may already have the Hornby maintenance sheet though that doesn't show much in the way of wiring. In general its a process of deduction by inspection. The wiring between the loco and tender has two functions, one pair carries the current pickup from the wheels to the decoder socket in the tender. the other pair feeds the motor from the decoder socket.

The decoder socket is wired conventionally.

BTW the best place for this request for information would be in the Modelling Questions, Help and Tips forum, rather than here.