you sort it tubs? if not, merlin motorsport, and redline motorsport were cheap if i remember correctly from when i was planning on building a stock hatch race car myself.
Sometimes Rally Design are very prompt with mail order, my Hawk pads and beam bushes came the very next day Tub, I didn't think you'd be fat enough to fill an OMP RS
Ask shells Dad !! Where i got all mine from ! And if your gonna do it get a five point - no point p****** about with toys if you have a proper seat ... Some sort of bracketry needs making to get it mounted to the floor, or hack the floor up but make sure its good an strong. As for mot never had a problem ! If the buckle isnt fast enough then thats just bollox - i can undo mine faster than the old style whilts tripping over the door bar and banging my head on the upper bar of the cage, still beating the old type belt !!
Put it this way - when i smashed golfi up i was in the tubular seat and a three point harness. I had two days of due to bruising to my rib cage, my passenger (thank god) bless her just got shaken up. So i went the whole hog and paid out over 400 for seat harness and frames, he gets em direct from corbeau/cobra so it works out ok.
no one in my motorclub has ever had any problem getting an mot on a car with aircraft release type buckles or spring clip belt mounts on rally cars, what about westfields and other kit cars? if you have trouble with mot's take the car to a mot centre wich also logbooks competition cars - they will pass them no problem!
also, make sure you fit your seats/belts to the Motor Association Specs it could make a difference in the event of an insurance claim!