Here's one that should be fun.  A conductor friend of mine asked about
British orchestral variations for a possible CD.  I have bounced the idea
of the British Music list and the answers are still coming in; I thought
you lot would be a fruitful lot for some collective brainpicking.  So far
we have:

Malcolm Arnold
Variations on a Theme of Ruth Gipps

Arthur Bliss
Meditations on a Theme of John Blow

Havergal Brian
Fantastic Variations (on 'Three Blind Mice')
Burlesque Variations on an Original Theme

Percy Grainger
Green Bushes
Kleine Variationen-Form
(both recently recorded by Hickox in the Chandos complete Grainger series)

John McCabe
Variations on a Theme of Hartmann

Robert Simpson
Variations on a Theme of Nielsen (from the incidental music to Ebbe
Skammelsen)
(will doubtless be recorded for the Hyperion Simpson series)

Ronald Stevenson
18 Variations on a Bach Chorale
Simple Variations on Purcell's 'New Scotch Tune' (6')
Variations Vocalises sur deux themes de 'Les Troyens" (Vocalise Variations
on Two Themes from 'The Trojans')

Cedric Thorpe Davie
Diversions on a Theme of Dr Arne

Ralph Vaughan Williams
Variations for Brass Band (orch. Gordon Jacob)

Any more for any more? I'll post the complete (ha!) list when your ideas
are all in.

Cheers

Martin Anderson
Toccata Press
http://www.classical.net/music/books/toccata/