For starters, my deepest sympathies Andy.
From my experience, the TLR is the toughest to adjust to, now that my eyesight is getting worse. With my SLR & rangefinders, I can usually diopter my way around the problems, but so far I haven't found such a solution for the Rollei. Right now I'm doing the strong prescription reading glasses, with the pop up magnifier, and a stock Rollei screen, (which although dark, gives me that "pop" when the subject is in focus, which I can't seem to get with a Maxwell screen, not with my eyes anyway). I use the magnifier, and my strong reading glasses to get the subject in focus, then fold back the magnifier and frame the shot, while still wearing the reading glasses. Not the way I like to work, but so far I can still get decent images this way.
Good luck with whatever you decide to do Andy.
Best,
-Tim