sorry if this has been covered before but i couln't find anything using the search function
today i replaced the driver seatbelt with a new one from JK. all went fine, but the bolt holding the end of the seatbelt in the arch area next to the seat was very stiff. gave it some stick and it shifted, and came out ok and the anchor point seemed fine once the bolt was out. fitted new one fine, but then when i came to the passenger side the same bolt wouldn't budge, finally it did and broke the weld on the nut under the panel. looking underneath it seams that the lower panel has rusted under the underseal, and the anchor bolt has snapped off - luckily now and not in a crash! anyway i've got a loose seatbelt bolt with a nut rusted on the other end but on the wrong side of the panel (it wont pull through as the top bit of metal seems good)

anyway - my plan is to angle grind off the top of the bolt and pull it through to get the old seatbelt off. but to fit the new one i'm very dubious about bolting it to the wheel arch panel given the rust there. is there an alternative anchor point that can be used for the end of the seatbelt? i was thinking of somewhere on the b pillar, lower down from the reel as it can be accessed from inside the b pillar to fit one of these anchor plates which i use to fit my rear seatbelts

the question is - would this be fine for MOT and has anyone done this previously for advise? the B pillar seems a hell of a lot more structurally sound on my van so surely would be seen as being more safe?
thanks!