My seat runners arrived in the post;
I thought they would need adjusting but I lucked out - perfect length, 330mm, and the adjuster bar just needed a little gentle bending to change from 290mm width as sold, to the 300mm width of the seats:
These were from Ebay/KDR Seating, now I have them in my hands they look identical to the CBS ones:
Of course - I don't have the right bolts to fit it to the car - I need some M8 40mm (possibly 30mm?) Cap head screws...