No worries, glad to help.Sandyb, thanks for that, all sorted with the 3/32 Allen key. I was going to use the small lead split shot fishing weight to do the same trick as the brass spacer!
A piece of small lead shot works too.The correct hex size is 3/32". As stated above I bought a set of 5 reasonably cheap. Irwin part no. 10584.
I also contacted RCBS in America who also sent me free replacement grub screws, but also some really small punched brass spacers to put between the grub screw and die body. These stop the thread cutting into the grub screw as you try to rotate it potentially resulting in stripping the hex.
Hope this helps.