Thanks very much for your replies and your suggestions, they are much appreciated. I am sorry it's taken so long to write back; we've recently had a baby and so I don't rule my time as I used to be able to...
Duncan, thanks for mentioning split reels. That seems a very convenient way to keep the film organised while spooling. I've found this one on the US Ebay but I haven't found any sellers of such reels here in Europe.
I guess I should try to find a few film cans as well to hold, say, 1/4 each of the 400' roll. Then I could more easily load film into a 100' bulk loader, which I've seen are quite readily available.
As for changing bags - I've seen a Calumet pop-up changing "tent" which offers vertical room. And over at the Project Double-X website there's a reference to cotton changing bags sold on Ebay by Roger Luo. Does anyone have experience with either of these items?
Lastly, what about film cassettes? I've seen that people use old empty film canisters. Is that preferable to other cassettes? I actually have two IXMOO for my Leica II but for my M6TTL I'll need to use something else.
Cheers and thanks for your help