"A Natural History of Ferns" (Robbin C. Moran) might be useful.
I also like "Fern Grower's Manual" (Barbara J. Hoshizaki & Robbin C. Moran) and "Encyclopedia of Ferns" (David L. Jones).
Are you a member of the British Pteridological Society?
They often list publications that appear to be interesting.

If you have an opportunity to travel to the Southern US, we have a Georgia (State) College Botanical Garden near Atlanta, that has the most extensive collection of the world's hardy ferns in the US and the collection is probably rated in the top 3 in the world.
Rb

Here is a link that might be useful: BPS-Special Publications

Thanks Razorback,have made a note of those titles. No i'm not a member of the BPS but regularly visit their website

Another more recent is by Sue Olsen - "Encyclopedia of Garden Ferns". I use it often. She has grown ferns for many years (decades!)-- in the state of Washington, and has wide knowledge.