Sibelius 7 to LilyPond Conversion!

[Thomas WillNot]

Hello,

I have a multi-part band score in Sibelius 7 that I have been trying to
convert to LilyPond format. (No, not the original Sibelius 7 for RISC OS,
but rather the newer Sibelius 7.1.3.77 for Microsoft Windows.)

I have exported it into the MusicXML exchange format and attempted to use
the MusicXML2LY program supplied with LilyPond with no luck.
It will read the XML file but then spit out a bunch of complaints, but no
LilyPond file is produced!
I tried splitting a single instrument's part from the main Sibelius file,
then exporting just that and running MusicXML2LY but that didn't even get
rid of any of the errors, never mind produce a file!
I read elsewhere someone having this same problem recently with the same
versions of Sibelius and LilyPond I am using (7.1.3.77 and 2.18.2,
respectively), and they were suggested to try Denemo, which apparently uses
its own methods for conversion and its own of LilyPond.  I'd never used it
before, but I gave it a shot, and it's a really bizzarre program in every
way, especially on Windows, but I figured it out and was able to actually
produce a file!  It does the conversion its own way adding a lot of strange
wrappers, which can be easily removed, however my biggest problem is that
everything is converted in absolute mode.  If I were using the regular
LilyPond MusicXML2LY program, I would simply run it with the -r option, but
I don't see how this can be done in Denemo.
It also adds staccato and other markings with "-\staccato" or "-\markup" - I
don't know the purpose of the hyphen, but it makes the file fail if your
remove Denemo's weird wrappers and other commands.  This should be
changeable with Find & Replace, but still my point is that it'd be nice if
LilyPond 2.18.2's MusicXML2LY just worked! :P

Of course I could manually remove all the octave markings but there are
about seventeen pages of music I'm working with so I'd love to hear of an
easier way.

Thanks,
    Thomas