...how can I tell if it has had the emissions update?

If you go onto Seats web site and look for emissions update they have a place where you can put in the cars VIN number and they will tell you if it has been updated. If your car has been in a main dealer for any reason it will have been done. A failed EGR valve within two years of the update wave been replaced free or in many cases refunded if you have already paid.

Every time my Skoda goes to the dealer I'm asked about the emissions update and every time I refuse.

Your lucky Bromptonaut there are hundreds of thousands of VAG owners who had the fix applied without even being asked and plenty who had it applied even when the dealer was told not to. You must have one of the better dealers.

Steep? Almost vertical!! A salutary lesson here.....so much unnecessary work. Air and pollen filters can be cleaned with a stiff brush (the ones in our 18yr old Focus are original), coolant does not need to be changed......and as for the totting up of seals, rings, bolts etc - the mind boggles. Thank goodness I learned how to service a car as an impecunious student. I bet they didn't bother to clean and grease the brake pipes.

I'll leave debate about brushing out filters to others but the seals, rings etc are presumably required for a dealer standard repair. If you or I want to chance re using seals that's out prerogative but not what I'd expect in a franchised workshop.

I suspect the coolant needed to be drained as part of the EGR replacement. Is it possible an EGR cooling fault could cause coolant contamination so that replacement is advised.

Its not really a warranty its called trust building measures and unlike a warranty its at VAG,s discretion, you get no paperwork so there is no record of having been done and VAG can hide the figures, and there is no warranty on the replaced part. I know of someone that had four RGR valves replaced within the two years and at two years and three weeks VAG were wanting £1400 for a fifth.