TOLD YA
dont sell yaself short on the building of ya own mate, if you can shoot and ferret, Im sure you can use a hammer or screw gun, get a cheap 6x4 shed as suggested, panel the inside and put a section 24" high across the door opening (stops them escaping when door open) you can easily step over this on entering court,
although that one you have linked to looks good, its starting at £170 cant see in his feedback what they normally sell at, or delivery charge
plus it would still need raising up, or that floor will rot in a year or two
£285 Delivered and installed for that