Upon a winter check, I noticed the tyres (Conti 275/45 R21 110Y) are all around 3mm. I know this is a subjective question - do you believe it's worth changing them now or wait until they get closer to the 2mm mark?

I always change my tyres at 3mm. MY16 RRS 3.0 SDV6 HSE Dynamic

I thought once they were getting towards 3 mm they were no good or no where near as good

I always used to change summer road tyres at 3mm. There is evidence that from 3mm down, the tyre's performance in wet conditions deteriorates quickly.

Winter tyres should be changed at 4mm and usually have a wear marker for that depth.

ATs would be changed once they start to struggle with the conditions they are most used in. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Interesting I decided to put my OME wheels and tyres back on yesterday. My car had 22 inch wheels that I had changed down to 20 inch so I could put some better multi purpose tyres on. I used a battery powered rattle gun, made life easy and will carry this in the car from now on . Also decided to fit my rear mud flaps, had them for two and a half years, easy job. Very heavy wheels and lifting and lining up is mot an easy job, can see this almost being a call out as I get older. Good chance to check brake wear as well,all good in that area. Got 75,000 k's out of my Coopers, front were worn on the inside edge and needed changing.Car is nice and quite on the road again ready for our Christmas get away. M16 SVD8 ,4.4 HSE with a few extras, Sold R50 , Wife SQ5 , BMW R1200GSW.

Thanks guys.
I thought I would double check my measurements this morning, only to find out I hadn't properly calibrated my tyre depth gauge.. now the lowest reading for all 4 tyres is 3.8mm. Looks like I am ok for another few miles and can fund more mince pies