I largely agree with Colin on Bliss, but am more sympathetic to the Colour Symphony (especially in recordings by Bliss himself and Charles Groves.) Even a review of the first recording of Morning Heroes stressed that "one looked in vain for base metals being transformed into gold" and, in this respect, the work was compared adversely with other British choral works like Howells's Hymnus Paradisi or Vaughan Williams's "Dona Nobis Pacem" or Britten's "War Requiem" (even Dyson's long-winded "Quo Vadis" has a metal into gold bit at the end IMHO.)
Nevertheless, I don't agree. The return of the timpani, symbolising the cannon fire over the Somme, at the very end of Morning Heroes is certainly a goose-pimple moment for me, which I find terribly moving in view of the fact that the work was written to exorcise nightmares of the Battle of the Somme, where Bliss's much loved brother, Kennard had been killed.
If you can find a copy, Bliss's book "As I Remember" is one of the most enjoyable and informative composer autobiographies.
As I mentioned before, the Oboe Quintet is a lovely, oddly haunting pastoral work of great appeal and like some others here, my favourite works by Bliss are the Meditations on a Theme by John Blow (I was delighted to see Hugo Rignold's/ City of Birmingham SO unrivalled Lyrita account restored to circulation recently), Things To Come (Bliss's own recording is my favourite) and I am increasingly enjoying the late Metamorphic Variations, which grows on you I think.
I also do not rate him as highly as VW, Bax, Moeran, Brian and Rubbra, for example, but some of his works, do, I believe, achieve a level of greatness.