I've got a pair of seatbelts in the garage that I was going to put in the back of my 110, but decided that they weren't going to be much use on side benches (and they're not needed for MOT) so I've never fitted them. I seem to remember they're 3 point inertia reel, but I'll have a look in daylight and let you know.
Bob
1990 ex-RAF 110 3.5 V8 17KJ83
1967 3/4 ton Sankey 09ES17