Rear suspension is very hard

[gordonmc]

I was given a dead 2005 Berlingo box van,  an MOT failure due to collapsed rear training arm bearings (common fault from what I gleaned).
When I got the axle off I found the torsion bar had snapped in two places and the bearings were well and truly gone.
I acquired a replacement rear axle which, I was told, came from the same model and year of scrapped van and was a good 'un.
Swapped the axles over and it looked good, so I felt OK about spending a bit more money. Replaced all the rear brake pipes, an ABS sensor, alternator, and battery. The rocker box (leaking) was resealed and the BSI was reset.
The van went for an MOT last week and passed with no advisories.
However, the examiner said although it wasn't an MOT failure issue, the rear suspension was hard as a hard thing.
Driving it only the open road confirmed it.
I suspect, and would welcome thoughts, that the replacement came from a higher load-rated vehicle with beefier torsion bars.
Jumping on the rear of the load deck does move the body in relation to the wheels, so the trailing arms are moving radially. Shocks are not seized.
Thoughts?
What to do?

[dumdum]

Get some new or used 600kg torsion bars (yours will be 800 bars I'd think) or live with it are your options buddy