Chances are, that there is rot at the rear of the spring hangers [xx(]
The chassis meets the inner rear corner and joins up with the rear door pillars, just behind the lower rear corners. This is an mot fail, due to the proximity of the suspension mount.
You have to drop the petrol tank to get into the o/s one (not a good idea welding near the tank anyway [B)]
http://www.commervanspares.co.uk/
http://www.yorkshireclassiccampers.co.uk/