Hi again joejack,
I've alraedy done all the loose/play checks prior to this to rule out any of the LBS people mis-fixes. The bottom bracket is solid all the way round. I've also free spun the cranks, there was a degree of harshness in the driveline with ticks and clicks every now and then, but that was with the chain on. The harshness didn't go away even if I freshly oil the chain. With the chain off, the cranks free spin butter smooth.