Hi Jeff thanks for your reply.
Yep I checked multiple websites and this one comes back as not compliant, based on what's on the V5C that makes sense.
To be compliant (for now) NOx just needs to be below 0.08g/km.
I expect if your 260 is coming back compliant it probably has these numbers in the V5C under 'Exhaust Emissions':
CO: 0.723
HC: 0.092
NOx: 0.027
Is that something you'd be able to help confirm?