After fiddling about with an old manfrotto plate whose screw had fallen out, and trying to find a large enough flat head screw that would go through the RRS clamp, to the manfrotto plate, to the manfrotto clamp and then into the head.......and failing miserably......
If anyone is interested, firstly use your hands and eyes instead of trying to be clever. There is a large lip which protudes from the manfrotto joystick head which means that the RRS clamp can not be lain on top, the head isn't flat........unless of course you mount it sideways in which case it slots in perfectly!!
I hadn't tried that of course, far too easy. It means having to use the joystick head with the trigger facing the palm of your hand (270 degrees instead of 360) but it's a minor inconvenience, i got used to it within 20 seconds and it's a real pleasure to use a good joystick head mated to the truly excellent RRS lever clamp and L plate. Heaven sent for social photography where you need to focus recompose and shoot fast and intuitively.
It's also a lot cheaper than having to buy the overpriced Kirk adaptor, thanks for the suggestion though.