JK Composite Seats - anyone got any to try?

[HughS47]

I'm looking at fitting some JK composite seats in our MX5. Their R4647 seat fits directly onto the runners, but after a fiasco with some Monaco Pro seats, i'd like to try them first.

Does anyone have them fitted to their machine so that I can come and try them for size before buying - they're based in Merseyside....