Well, that produced a nice collection of errors:
Spoiler:
2 Value Error : font-family Property font-family doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : "LinotypeDidot RomanSC"
3 Property src doesn't exist : url(fonts/LinotypeDidot RomanSC )
6 Value Error : font-family Property font-family doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : "Didot LT Pro Italic"
7 Value Error : font-style Property font-style doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : italic
8 Value Error : font-weight Property font-weight doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : normal
9 Property src doesn't exist : url(../Fonts/DidotLTPro-Italic.otf)
12 Value Error : font-family Property font-family doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : "Didot LT Pro Roman"
13 Value Error : font-style Property font-style doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : normal
14 Value Error : font-weight Property font-weight doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : normal
15 Property src doesn't exist : url(../Fonts/DidotLTPro-Roman.otf)
18 Value Error : font-family Property font-family doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : "AppleGothic"
19 Value Error : font-style Property font-style doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : normal
20 Value Error : font-weight Property font-weight doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : normal
21 Property src doesn't exist : url(../Fonts/AppleGothic.ttf)
It doesn't help that Jutoh produces a very long css file, full of styles I'm not using, which makes it harder to spot what's going on with the ones I am using. Given the amount of clean up that's needed to make it work, it looks as if creating the css myself in the first place would be just as easy, which is a shame, because I really liked the idea of not having to delve into all that stuff!
The first couple of errors are because the font was PS not ttf or off, so I just need to find an alternative.
I haven't worked out yet how to fix the css1, css2, css3 comments but I'm sure I'll get there.
I'm puzzled by the "Property src doesn't exist : url(../Fonts/DidotLTPro-Roman.otf)" &c because as far as I can see, the path and the filename match what's there

.

It's like finding myself back in 1985 trying to do word processing before they invented WYSISYG. As long as I don't have to go back to DOS!