I had a horrible feeling that one of the shocks had gone in a big way.
Turns out the single bolts connecting both ends of my hotchkis sway bar to the suspension had come loose
One had fallen out completely and the other was nearly out too despite both being loctited in 
The one that had fallen out completely had allowed the bar to move forward and rub on the drive shaft causing the noise. Given enough time I reckon this would have milled right through it!
Suffice to say, if you've got a Hotchkis, check the bolts!
