Rich,
I have put 1 shim on the blue spring which was slightly better but still juddery in some cases so still not ideal, maybe my blue spring is tired though... so i contacted Forge and bought one of there Valve Tuning kits, all available springs and a pack of Shims

....once i get my car back from Waynes i will have a play see what i can come up with, should be able to get something sorted with all the below!
Cheers
Ian