Mini 1.4 First Idling issue

[ChampyS]

Have a Mini 1.4 First Petrol '59 plate with Start/Stop. It has an issue idling and moving in slow traffic. The idling is varying whereby you can visibly see the needle moving slightly and it is almost stalling in slow traffic in the mornings, but the car is in gear and clutch up, so not start / stop activating. It has recently been serviced and had a new AGM battery. I have seen some questions over the VANOS solenoid being to blame.

Anyone got any ideas please?