Just switched back to my 18" wheels and summer tyres and the ride is better.
I don't really understand why, winter tyres do have a higher load index 97 and 99 compared to 92 and 94 of the summers.
I borrowed my neighbours car today, e93 SE spec with 17" run flats. The ride was more to my liking if not the body control.
I'm seriously thinking about fitting SE suspension with uprated ARB's as my next experiment.