Andrew Owen has released four additional pieces from the U3.5: Pax Britannia soundtrack on the Ultima Dragons Facebook group. The four pieces are the Dungeon theme, the Combat theme, the Castle theme, and a reworking of Stones.

And an interesting note about Stones:

This is the actual PSG (AY-3-8910) version of the music from the character generation.

You can find all four tracks available for download Pax Britannia project entry. And you can listen to them there, as well!