Thanks for the help so far everyone
@Tyrias: yeah I've actually decided to change style to post rock/minimalism, especially considering one of the conditions is 'no synthesised keyboard timbres'.
The songs I've got currently in post rock are:
Godspeed You! Black Emperor - Rockets Fall On Rocket Falls
God Is An Astronaut - All Is Violent, All Is Bright
If These Trees Could Talk - From Roots To Needles
Mogwai - San Pedro
Explosions In The Sky - First Breath After Coma
This Will Destroy You - Threads
Will check that out wolf.
And as for Metropolis Part 2 I've got a few (eg the 5/4 riff changing to 12/8 in Beyond This Life) but it's far easier to explain things in the context of one song than one concept album that links back to a song on a different album.