Couple of things:
I'm nearly sure the 19" wheels use spacers to make them fit and this can lead to unusual handling qualities even though the lower profile tyres should in theory help. I believe as previously posted 18"s with Pirelli Scorpions appears to be the best handling combination.
If the MOT is anything like our DOE test (which I'm almost sure will have used the MOT as a template) it will not necessarliy identify bad shock absorbers. The pass/fail is based on discrepancy across an axle, If both shocks are equally bad it will pass whereas 1 good 1 bad on an axle will garner a fail. Over here 4 equally bad shocks will pass a DOE test. Fitting high quality gas shocks such as Bilstein or Koni will revolutionise the roll qualities of your RR.
As previously posted running at motorway height permanently should reduce roll also. If you have plenty money putting Arnott Gen III airbags under should stiffen it further.
Another rarely mentioned aspect to RR ownership (and indeed any permanent 4 wheel drive jeep I've driven) is how you actually drive the vehicle. You have to power these cars through a bend or they understeer and roll appallingly. Get your braking done before you turn in and when you get back on the power you will feel the car stiffen up and tighten its line. If you drive it like a front wheel drive car it will not thank you.
