They'll slowly appear on ebay etc again now the TI is stable. But look at soundcontrol.co.uk, I bought my TI from there.
If I were you I'd put the extra money up for the TI only if I was sure I could afford it,sometimes I find myself wishing I had just bought a C and a good sound card, but as the updates get better I find myself happy as can be.
By the way Hyper saw is currently so under-rated as it is hardly used, most of the patches are still using loads of unison etc to get phatter sounds, but I think that'll change soon. (Is it normal for access to release new sounds with later OS releases?, there are still 2046 patches in ROM to be over-written)
As for MK2, Access are taking a lot of stick at the moment because people are having problems, they will iron these all out before deciding if they will go to a TI-B or just change to something else, (imo)
This synth will never leave my set-up as I'm sure many people feel about the previous models, so it doesn;t really matter what you buy you'll love it, it only matters if you are the sort of person who has regrets and will sit an pine for the TI's features if you buy a C.
I have the full TI-K and I can tell you it has excellent keys and will be my main controller from now on, as it can also do remotes.
(pity I can't play the bloody thing

)
Cheers
Kris