The Tetenal RA-4 description says 2.5L though. That's probably what I'll do unless I can buy a smaller qty (not 50L!) of Fuji/Kodak chems locally. At least the Tetenal states the area of paper processed; I haven't read enough of the ektacolor docs to figure out L/m^2 consumption.
Further reading in the Kodak E-6 manual says that you can use the C-41 stabiliser as a final rinse on E-6. That, in conjunction with Tetenal selling just the one, makes me believe that bit will be OK.
OK, Fuji looks like a good option for the C-41 colour dev even if it does mean buying twice as much. You're right (checked the docs) that there's an E-6 colour-dev starter but Vanbar don't seem to sell anything like that from any of the brands. I'll definitely have to get pricing from the local supplies joint.
Final assumption: Fuji C-41 colour-dev + Agfa 70 BL + Kodak E-6 fix is a seriously mongrel process. It should all still work with no disagreements between their various interpretations of the process though, right?
thanks for all the help!