Update time -
Finally got around to fitting the Ragazzon and had a good look at the rear swing arms while I was under there. On the offside one, I wedged a big screwdriver in between the swing arm and it's bracket and CLUNK, it shifted sideways a good couple of mm, try it from the other side and CLUNK, back it went. Conclusion, offside swing arm bearings are knobbed, nearside seems OK but I'll replace them anyway. Well at least I won't be bored on my Xmas holidays.
So that's a problem found but whether or not it is THE problem only time, and another pair of Toyos will tell.
Ragazzon seems pretty good though.