Looked at a brand new octy TDi Sport hatch in the showroom earlier this year and yes the seat base puled forward and down into the footwell allowing the seat back to fold flat. The new car was a bit expensive for me though so I ended up buying a 54 plate 2.0 TDi Ambiente. Didn't notice until I'd bought it and came to load up the back one day, but that has a fixed seat base and the aforementioned 20 degree slope, bu***r. Dont know if its a spec level or an age thing but there's definitely two different types of seat base.

Does anyone know what it might cost to replace my park bench with one of the folding sort?

This 20 degree slope is a serious b*g**r

In Italy we've got 4 versions of Skoda Octavia: Classic, Ambiente, Elegance, RS. The only one with seat back folding flat is the Wagon Elegance, while in the other versions it is an option.