Steve, as you well know, farm machinery left outside in all weathers and unused deteriorates rapidly

I wasn't looking forward to driving the axle out of the roller through it's bearings as everything was rather rusty. I left the end where I unscrewed the bracket soaking in a bucket of diesel overnight to try and penetrate, and certainly that bearing came out nicely.
Firstly I screwed the bracket back on, and with a bit of wood packing in between, gave it a few thumps with a 14 lb sledge hammer. To my relief it started moving and that end's bearing fell out! This left enough room at the other end to thump the remaining bracket with the sledge hammer and slowly pull the 25 mm shaft through it's other bearing. I am amazed that the roll pin that retains this bracket to the shaft didn't shear - it got a lot of nasty thumps from the sledge - enough to bend it (you can just see this in the picture with the bucket of diesel. I need to detach that bracket to straighten it and also to aid re-assembly so the bearing doesn't have to slide the full shaft length.
So at last I have a bearing in my hand and can measure it. (25 mm bore, 52 mm o/d, and 15 mm thick)
I put the end that still has the bearing in the bucket to soak - the outer of this bearing must be very tight as all that hammering would have been trying to push it out. May end up having to cut it out.
I've just checked the main flail head bearings - can't detect any play so hopefully they'll be ok with just a normal lubrication - silly thing is there is no provision for greasing the roller's bearings, and I can't see any way to incorporate it.
So now to order the bearings, then I'll start putting the controls back together