Thanks for the help here, I've got it working this morning after managing to corrupt my installation last night and having to start again (note to self: back up save data regularly...)
For anyone interested in getting Daggerfall working, I ended up using the version of the game that comes with the Elder Scrolls Anthology set. I installed it on my Windows machine, and then copied over the folders DAGGER and DFCD into a folder called DF in the roms/pc/ path.
Edit the z.cfg file in the DAGGER folder so that the line for Path reads DF/dagger/Arena2
Then launching DosBox, do the following:
mount d "/home/pi/RetroPie/roms/pc/DF/DFCD" -t cdrom -label Daggerfall
cd DF/dagger
DAGGER
The game should launch fine.
Will set up a script to auto run this shortly, but I'm just happy to have it running.
Seems to run OK so far, but I've not hit any external areas yet so I expect there to be some degredation of performance there.