Hence the comments to fit 4 seater 4 LEAF springs Peter
Sorry Graham. I don't get your point. Basically all I was saying is that I would have thought 4 seater springs (intended for a Plus 4 or Roadster 4 seater) would be overkill and give too harsh a ride on a 4/4 2 seater.
I went for 4 seater 4 leaf springs from Mulfab (as recommended by both DaveW and by Peter Mulberry). The car rides really well now both solo and fully laden. A local road that used to be taken at 45-50mph max can now be driven at well over 70 when no one is looking.