Just thought I'd update this now I've finished the job and replaced the fan pulley bracket with a couple of observations for anyone searching in the future:
Answering my own question, the fan/clutch/pulley assembly does have to come off first to access all the bolts for the bracket.
After removing the aux belt I removed the fan from the clutch first (3x 5mm head hex/allen screws), then the idler puller (6mm hex) , then used a strap wrench as suggested here and in other posts to hold the fan pulley to loosen the centre bolt (8mm hex), then the 4x 10mm screws holding the pulley on. It was pretty tight, I had to tap it with a rubber mallet and gently persuade it off with a screwdriver from behind.
Cooling system then had to be drained to remove the heater pipe that runs across the top of the bracket & plugs into the side of the water pump, blocking access to the last bracket bolt, replaced the big O ring whilst there.
Then the easy bit which was old bracket off and new one on, then do it all again in reverse!
I used the Febi bracket, 14946, which fitted perfectly and from reading quite a few posts seemed to fit better than Meyle etc.
The bracket bearing hadn't totally failed, but was noisy with some play and had spewed all it's grease out of the rear seal.