Thanks to y' All.
Roger thank you that is exactly what I needed to know, so I've been out to try a couple.
Yes the hard case fits width ways at the very back of the Octavia (both hatch and estate) boot where it doesn't fit in most other cars. That's down to a bit of overhang behind the rear wheels and little/no obstruction of the pockets behind the wheel arches.
Anybody got any other candidates please?