It's time I invested in some new hand files 8"-10" size
I still have some very good smaller ones (CK) but I'm struggling to identify a good set of larger files
any suggestions 
Kennedy brand files from Cromwell Tools are very good.
Decent steel and properly through-hardened. (The cheap, don't-last files are usually low-grade steel that's been case hardened. That's
why they don't last.)
Available in every size, shape and cut you could ever need, and pretty reasonably priced, too.
Remember though, they don't come with a handle. Buy those separately.
No connection with the company myself. I just work in one of those jobs where we still do a fair bit of hand filing, and always get my files from them.