Accumulator won't make any difference to the ride quality.
Get the car on level ground. From out side does it look level front/rear and side to side? Is the front wing about 70mm above the tyre. Push down on each corner is there 6" + of smooth movement.
Put the suspension in low, allow it to settle and then into high. Does it go up smoothly with no creaking or groaning noises. In high when viewed from behind do the rear wheels appear to lean in at the top. Does the back go up and down as well?
Are all the roll bar ends securely fixed - especially at the rear?
When you fitted the spheres did you fit the correct ones - they all look the same and fit, but have different internals, which can ruin the handling.
Tell us what you find, and we can see if that helps to pin the problem down.
Loads of smooth movement at the back, almost certainly not 6" at the front. It goes up and down quite happily without creaks, although it can linger in one position for a few moments before rising/descending.
Rear wheels don't appear to lean in at the top, I will check this again.
Roll bar ends, no idea, how do I check, is it easy?
AFAIK they are the correct spheres, I didn't fit them myself, the chaps who service the car seem to know what they're doing, but I do wonder sometimes as they lose interest when there are slightly strange problems.
The car bangs over potholes quite badly but i'm not sure if this is normal. Large obstacles like speedhumps it takes quite gracefully, but I can feel almost every imperfection in the road, not badly, but more than I think I should. For example I can feel each rumble strip going into our village, even driving slowly behind a tractor, but I can't in a 206 from work!