Harry, before I answer, remember I drive a Midget not a B - there I said it
Looking at the diagrams in the link above and my on (Midget) charts.
If you look at the bottom of page 15 in about the middle of the page, the Brown/Red wire is for the "butt" seatbelt switch
Same page 2 X Light Green/White is the seatbelt switches themselves.
Green/Orange as mentioned is handbrake light.
I can't see either the Green/Orange or the Red/Yellow you mention. However, if you look on page 30 at the seatbelts you see some different colours suggesting that they may have changed over the years. In terms of the harness and the green wire - I have a few green wires dangling that my schematic doesn't account for but which are from the factory. The red wire is almost certainly a light of some description - is there an interior light somewhere that wants a wire?
good luck!