Hi John, welcome to TOC.
It is really impossible for anybody on a forum to be sure without experiencing the vehicle themselves. However, the Valvematic petrol engine has very little torque at low revs compared to a diesel - it will never seem as smooth as a diesel if idling along at low revs. Having said that I would have thought that the CVT would ameliorate that to some extent.
It has done only 20,000 in 7 years so less than 3,000 p.a. - maybe it needs a good high-speed run or 2 to blow the cobwebs out? 😉
Did it have it's sparkplugs changed at the recommended service (5 years iirc)?