May be of use to some.

[Simon 3.2M]

Carried out a service on the roadster today and as well as the oil I decided to change the plugs as I’ve not done them in my ownership. Below is a pic of those that came out - the wetness is penetrating oil, I spray a bit in just in case they have been over tightened. As you can see the burn is even and they don’t look too tired. I’ve noticed two things; she pulls much better and, this may help some, the revs dipping and coming back up when you dip the clutch has gone. This is something a few of us M owners suffer.
Hope this helps.

 

[Beedub]

alot of life left in those....... nice to see improvements from basic maintenance, enjoy

 

[Slideways]

How many miles were on those plugs?

 

[Argenta]

Good plugs makes any petrol engine better

 

[Simon 3.2M]

How many miles were on those plugs?

About 25k so not a massive amount but to me, I change most things on time of not mileage.