Tutors
Study Books
Brass Band Testpieces

There is a lot of stuff.

To get started Testpieces, in TC

Revelation (Wilby) parts 1&2
Paganini Variations (Wilby)
Sounds (Golland)
Muckle Flugga (Boyle)
Rococo Variations (Gregson)
Salford Sinfonietta (Barry)
Partita (Gregson)
Masquerade (Wilby)
Aeronauts (Richards)
Carnaval Romain (Berlioz arr Wright)
Symphony Of Marches (Vinter)

+ Assorted odds and sods

Study Books

Hovaldt Trumpet Technique
Stamp Warm Ups
Charles Colin Method
Charles Colin 100 Warm Ups
Otto Langey The Euphonium (TC)

Piano Accompaniments (There may be solo parts but some of my music is in storage)
Wiederkehr (Hartmann)
Rule Britannia (Hartmann)
Golland Euphonium Concerto 2
Oration (Snell)
Rhapsody For Euphonium (Curnow)
Fantasia (Jacob)
Demelza (Nash)
Golland Euphonium Concerto
Grandfather's Clock (Doughty)
On With The Motley (Leoncavallo are Farr)
Macushla (McMurrah as played by John Clough)
My Old Kentucky Home (Rimmer)
Varied Mood (Woodfield)
La Belle Américaine (Hartmann)
Pantomime (Sparke)
Andante & Rondo (Capuzzi arr Childs / Wilby)
Softly, As I Leave You album

There is lots more including several big Concertos with both TC and BC solo parts and accompaniment, but I need to find them, but off the top of my head include

Mealor Euphonium Concerto
Gregson Euphonium Concerto
Wilby Euphonium Concerto
Wynton Marsalis' Carnaval Album with piano accompaniment

As it's music it will probably cost a fair bit to send, but it's a decent collection that I have worked on for the last few years. Some of this stuff was expensive too.

I will update when I have the full list.