Hi

Planning to buy a used Sedan (do not prefer Estate styling) in the c.£15k range.

You don't get either Octavia or Superb as a sedan, the choice is hatchback or estate.

Or anything to watch for in Skoda models i mentioned.

The potential problem with your Skoda choices is the DSG automatic transmission. This is actually a dual clutch automated manual, and they don't stand up very well to harsh treatment. There is no doubt that they can be reliable, but that assumes previous owners have driven the car with some degree of mechanical sympathy (and you continue to). But unless you know the car, there is no way to tell how previous owners have driven it. There are also two different types of DSG, dry and wet clutch, the latter is more robust that the former but I'm not sure which models would have which DSG. I'd expect more powerful versions (petrol or diesel) to have the wet clutch type, but as said, I don't know.

Have also read reviews if Volvo sS60 but surprisingly they score 6/10 compared to 8 or 9 for Skodas.

No point in giving much consideration to reviews (unless owner reviews), journo's are unlikely to have the same priorities as a "normal" person. Having said that, since the Chinese got involved, Volvo's quality and reliability does seem to have taken a dive.

VW Passat was also on my radar but it’s discontinued now - it may cause reduced resale value.

wouldn't dismiss a Passat because of this, I don't see the depreciation being any more of an issue than if buying a previous shape or pre-facelift example of a current car. I would however be wary of the Passat because it uses the same DSG gearbox as the Skoda's.

Any other suggestions of cars I should look at?

Well they have been getting quite a lot of airtime on the forum of late, but the Mazda 6 is about as reliable a car of that size as you are likely to get (and that is actually a sedan), and that includes the auto!

I've had Volvos for years, they last donkeys years with a little TLC.