Originally Posted by Geo

Hi Lucille
The quick and safe answer is no, legal is the wrong term , MOT passable yes but not safe
if you can imagine under the vehicle there is a steel chassis rail running the full length both sides, the mounting points should in all honesty go to those, not necessarily direct though you could use the wooden panels if and only if the wooden panels at the same mounting point went on through the floor to the chassis.
my reference to being able to lift the vehicle from a seatbelt mount was not made in jest, any reasoably equipt and trustworthy work shop shop will be able to suggest suitable mounts and install belts for you on the reqd seats
Geo
Another alternative is to go through the floor anywhere suitible and put spreader plates on the out side again welded to metal structure