Thank you, luqmaninbmore
I just tested it with one .prc file I had converted using Mobipocket Creator and it does exactly what I want - ie opens up in FBReader so I can read with my usual font settings, page turns are speedy (very speedy in comparison with the original .pdf file) and it recognises the table of contents.
Brilliant - and being a .prc file it should also work with our new Kindle which means everything's pretty much in synch
Now I need to convert the rest of those horrid .pdf files!