It should have a socket, as Richard says, under the dash. Usually in the drivers footwell, but could be on the passenger side too! It looks like a SCART socket that you'd find on the back of a TV.
I have a diagnostic reader and live near Petworth - it wouldn't be a huge drama to come out and meet you. Can't guarantee that my reader will read your engine, but it's likely it will.
It's probably an oxygen sensor - that's a wild guess.
