Within reason, you should still be able to process C41 in batches of 4 rolls x 2 runs in a Jobo with rotary processing using one a shot developing system for virtually perfect results. This is using a 1510 tank and a 1530 extender to make the 1540 tank. This takes 470ml (I use 500ml) for 4 rolls of either 135 or 120. This is about the most economically expedient way to do C41 in a low end Jobo processor. Assuming you have the 1520 tank, then rotary processing doing 2 rolls with 250ml of chemistry also works out, but is a bit of a time killer.
C41, will do 8 rolls per litre of developer. As for the Tetenal product, I don’t know.
I assume you are not in Melbourne, otherwise you wouldn’t mention interstate freight from Vanbar.
I would be tempted to talk to people in a lab still doing C41 processing, ask about their chemicals and how they are broken down. I almost always purchased Kodak Flexicolor 5 litre kits for big film processing jobs; essentially they were two by 2.5 litre kits. Best of all is that they had a bleach and fix step, not a combined Blix, which is (was) a trade name of one of the American manufacturers, cannot remember which one. You may be surprised at what is inside some of these kits, some kits really were user friendly for breaking down to smaller mixing.
You could of course telephone Vanbar and ask if they know if it is possible for you to break up a large kit to a smaller kit, instead of mixing up the entire kit. Generally, I found that if at all possible, most kits were able to be broken in half.
Another possibility, you could try divided C41 developer. I myself have never used this, but a photographer living in the sticks did use this with, as far as I remember, quite acceptable results.
http://photo.net/film-and-processing-forum/00GxUf
I even printed some of his negatives using the then new RA4 process, everything seemed to work well and we made some very good colour prints.
I have the chemicals to mix C41, haven’t done that process for maybe 4 years, but I could get back into it after a day of fiddling and mixing chemistry and probably new batteries for the pH meter.
Vanbar have an online portal for bulk chemistry, I know that what is there is not all of what they have. I looked and could not see CD4 (colour developing agent 4) for C41 chemistry, but last time I bought CD4, I bought it from them, which would have been around 8 years ago and it wasn’t in their online catalogue then either.
http://www.vanbar.com.au/catalogue/index.php?item1=CHEMISTRY&item2=BULK&brand=
A 2.5 litre kit will let you develop 20 rolls of film at $5.25 per roll, plus any delivery costs. I would call that viable just on the fact you will (should) get perfect processing using a one shot developing technique.
Mick.