It appears that my car is set to fixed servicing.

What time frame does this involve every year or every 2 years?

I anticipate relatively low annual mileage so if every year then variable servicing would seem to be better value. I have been told that once you switch to variable servicing you can't then go back to fixed.

Presumably fixed would be beneficial to very high mileage drivers?

1 year or 10,000 miles, whichever comes soonest. If you are on fixed, you can't switch to variable (at least, that was what I was told when my car had a few fixed services done). No idea if the same goes for other way around.

Presumably fixed would be beneficial to very high mileage drivers?

No, the opposite. Variable is beneficial to high milage/motorway miles drivers. If you do less than 10,000 miles a year, I'd stick it on fixed.

2 years on the Octavia 2 for the inspection on fixed regime.

2 years on the Octavia 2 for the inspection on fixed regime.

That's another thing to add to the list of 'why to change cars'... didn't know that

Mine is going in in June for its first 12 month fixed.[8500 miles] Should I tell them I just want an oil /filter change with the good stuff? If I get it done at a good local garage will the warranty be okay?

As long as the service is carried out as laid out on the Skoda service sheet you can get it done elsewhere. A downside of that can be without trained Skoda techs doing the work they might not pick up and potential problems you may have as they wont have access to the latest information from Skoda. They will also not be able to check if your car is due any recalls etc.