I just pulled apart a friends ballast puppy to see why it was running slow. I pulled the bearing and it was 608zz, not a 627 as previously thought. So I went to the bearing shop and bought a new one, when I tried to install it on the shaft, the new bearing just fell on.
I measured both the original bearing and the new bearing, (both are 608zz) and new one was 7mm bore, 22mm o/d and 7 thick, which is correct as far as the spec says, however the original was 6.92mm bore, other dimensions are the same. I don't know how or why the original has a smaller bore than its supposed to.
I'm going up to my cabin on the weekend so i'll drag out all my old spare pump parts and check this out further.