Thanks everyone you've helped my make up my mind, well as much as I ever do anyway.
Taking all you say into account think I'll save my leather from the dylon and maybe use it for lining fabric instead. That is if my curiosity doesn't get the better of me or need one off paler colour. If i do i'll post pics.
Terry, I think your right in that they've been discontinued, the ones I have are pretty ancient. Another reason not to maybe waste leather by using them.
Removing the salt residue, which off course would likely precipitate on the leather (obvious now you mention it), may be one wetting too far to be worth it or to leave leather in condition that will work well.
Thanks again.
Gill