Removed the old BB today and the shell was full of grit/water, it was packed up against the back of the bearings. Given that the Sram external seals look like an ok design I think the real issue is water ingress thru the internal cable runs. Drive side was seized solid.
The Hope replacement uses a screw in centre tube that should solve that issue.
The Hope special tool is £40 but I used the usual stud/washers to insert the cups and a 30mm across flats bolt to screw in the centre tube.