Wheeled bike into the hallway and stripped it back down. Guess what? one of the friction plates is slightly bigger on the internal diameter. This plate goes after the anti-rattle spring. Re fitted and all working. Hope this may help someone in the future.
Ah yes, that'll be second friction plate you pop in.
If using Genuine plates, there's three different friction plates. 1 pair for first and last. I big larger internal diameter for spring (comes second), then the all the others. Parts diagram on Fowlers site pin points exact part num of plates to go where in what order.
What brand of plates did you go for in the end?
I tried EBC friction plates and springs. The heavy duty springs were shit, insane clutch grab once warm - couldn't keep bike still with clutch fully engaged and front brake on, let alone find neutral! I'd be at traffic lights fighting between a burnout or stalling, perpetually flipping between 1st and 2nd trying to find neutral, before giving up and hitting the kill switch...
EBC plates and genuine springs - got clutch slip...
EBC plates and original old springs - was about manageable for a 9 months before it started slipping again.
Got NOS genuine friction & steel plates from ebay (hunting down specific part nums, as some plates are shared with other bikes), with new genuine springs, and all lovely smooth, easy going clutch now with no slip or grab.