[GeraldG]

Thanks guys. I've located a couple of plugged holes where you expect them to be - in the floor pan in the cargo area about the mid point of each seat. But there is no threaded plate fitted which you'd normally expect to see.
The holes are directly above a chassis box section which have corresponding holes in the bottom of it.
I've found an owners handbook on ebay so hopefully that'll shed light on my problem.
In the meantime I'll keep looking.