That multi-way is for an early iPod.
It plugs into a module bundled tight behind the head-unit and that module has another long lead plugged into the head-unit’s Aux connector next to the Aerial plug.
I took it out and replaced it with something more useful as here
The OBDII socket looks a bit like an old TV SCART socket and is right at the end of the dash, next to the bonnet and boot release buttons and almost under the A-pillar.
This pic is looking almost straight up from the floor.
