For anyone who fancies usung their chrom for, say, Irish tunes, Brendan Power has just released a tuition course that takes you from alpha to omega. For the first part of the course you need stock chroms in G and D, and in the second part, which you buy separately if you want it, he deals with alternative tunings and so on. I'm familiar with the first part and can thoroughly recommend it. Note that he does not recommend the use of a C chrom for everything in this kind of music, laudable to some though that ultimate aim may be. Take a peek at his website.

As for high-pitched F harps, no problem. Buy a low F. The major makes all do them as far as I know.   Also, I use a low D harp for Irish tunes, never a standard D.