Parts are still in progress, I was out of town for a while and have to pick up again where I left off.
Note that there’s no need for a custom instrument transposition for the “Bass flute” part. Dorico already has a transposition for that instrument. Holst just used the wrong name. A “bass flute in G” is a weird name for an alto flute that I guess was commonly used in the U.K. (and nowhere else).
You might consider using the modern names for several instruments:
- “Bass flute in G” → Alto flute
- Tenor tuba → Baritone/Euphonium
- Bass tuba → Tuba
- Double bassoon → Contrabassoon
And ideally, put the euphonium part in bass clef and in concert key, which is what the vast majority of players will expect, rather than in treble clef B-flat, which is mostly a British brass band thing, plus a few trumpet players who changed instruments.
Also if you’re generating parts, ideally create both C and B-flat trumpet parts, since the latter is far more common.
And after I said this, I found that the same thing had been said earlier in the thread, but because this forum does something very weird with the HTML where Command-F to find in the page doesn’t actually work, I had no idea. 
91, 92: English Horn: last note should be D sharp.
Which movement?
Sorry, I assumed that replies would link to the original post. I was correcting your previous statement that it should be a D-flat (which would be the same as the note before it).
As an aside, I really hate not being able to hit Command-F and find things in this forum. It makes it very hard to meaningfully search the thread. 
Took me almost five minutes just to answer this simple question that should have taken one second.
Mars.
MARS
135: Bass Tromb: Slur missing.
52: dim hairpin missing in Piccolo 1.
91, 92: English Horn: last note should be D flat.
Should be a D-sharp.
Ah: I made the correct correction, but just wrote flat in the post.
I disagree with the naming of the tubas.
The unspecified Tenor Tuba (as Richard Strauss called it in “Heldenleben”) gives the conductor the choice and the opportunity to consider the instrument that best suits his/her vision.
Must be Browser specific. Command+F works fine here. (Waterfox on MacOS)
Command/Ctrl as such works, but searches only avalable text.
When you open a topic, only the last x posts are available, older ones only become visible when scrolling up.
So the text “nice open-source Dorico version” can only be found if you scrolled up to the first post, not directly after opening the topic
And, if you view the first post, the last isn’t visible, so text there cannot be found too.
I’m torn about this. On one hand I like to know what the original composer had in mind. On the other, it’s possible to run into things Dorico might not have a clue what it is and how to assign an instrument for playback.
Maybe there’s a way to pick more conventional instruments for the sake of the playback engine, but keep the historical names and contexts? This would be my choice for the main score (keep it historically accurate where possible).
The wonderful thing about digital scores in an editable format is we can quickly and easily transpose’the parts’ as we see fit before printing them out. Conductors are constantly needing to cue off parts to different players and instruments and it’s ‘easy’ to do with something like Dorico.
Like I had said above, my plan for the “Tenor Tuba” is to keep it named that but have it as a renamed euphonium for playback, possibly placing “(Euphonium)” in parentheses on the part name next to “Tenor Tuba” and on the instrument list just to show how it is normally played these days.
The research I was doing previously had indicated that there was actually for a short time an instrument with this name and it does not survive, and it was neither the euphonium nor a Wagner tuba, and it was this now non-existent instrument that Holst wrote for. So I didn’t want to completely remove the name “Tenor Tuba” in this particular case because it might inform a performance on a euphonium where the performer might not want to play it with a typical euphonium tone.
The other cases are more straightforward instances of an instrument name changing since Holst’s time but it is the same instrument, so those I would just rename.
I’ve updated the score on my website with 1 small correction to the notes, and one change of instrument: I’ve changed the Flute to a “Dorico standard” Alto Flute, but renamed it Bass Flute, so that playback templates will assign it correctly, but the name will still be as original on the page.
The Double Bassoon was already a “Dorico standard” Contrabassoon, relabelled.
Thoughts on Tenor Tuba
The standard British Orchestral tuba at the time was the Barlow British F Tuba. It is likely that Holst would have wanted something similar but in the Tenor range. Below are photos of a Barlow F and a Bb Saxhorn Bassse both made by Besson. The similarities are clear. The likelihood that the Saxhorn Basse was the intended instrument is high.
Photos courtesy of the York Master Archives
Barlow F Tuba
Bb Saxhorn Basse
Not being a brass player and not really having significant knowledge of brass instruments, how are these two horns different from the Euphonium, please? Even at my age I like to learn new things.
The Saxhorn Basse and the Euphonium are synonyms.
The F Tuba is a Bass Tuba, often used in orchestras for the Tuba* part. It’s a perfect fourth lower than the Euphonium – in opposite to the B♭ Contrabass Tuba which is an octave lower than the Euphonium.
* Generally Concert and Military Bands prefer E♭Tubas.
Thank you, @Vadian! I’ve learned something new today.
Not quite. Although they are both Euphonium (Tuba) Class Instruments, the Saxhorn Basse has a slightly lower conicity. This gives it a more direct sound and is capable of more bark in the tone.
Interesting…and good info for those of us who may orchestrate pieces where one or the other are used.