Disco 1 Are harness road legal

Ok I'm sure this could have been discussed in detail but upon searching I find wireing harness not quite the harness I'm looking for
I was originally considering trying to fit td5 rear seat due to the 3 cross belts as I have 3 kids and not being keen on lap belts but from what I have read it seems it's a real ball ach to do so I'm toying with another idea what could be stupid if so sorry
Ok so Soon I'm haveing the boot floor replaced as its show early onset of rust so if I beef up the area with stronger anchor points in the floor could I fit a 3 or 4 point harness either just for middle seat or all rear seats and maybe just maybe as I'm looking at this option maybe improving Dixie seat belts

Correct, has been discussed more than once in detail in most D1 forums.
Vehicles to day the rear center seat belt has a three point fixing with one the inertia reel fixed with in the roof space, so try doing that on a D1.
You could fit a fixed rally style belt to the rear center seat with a single strap with is anchor though the boot floor to a chassis mounting point.
You'll will be the first to find a way of improving the side facing boot seats from what they are now.