Simpson is an interesting composer who would surely repay study. His focus is on the large-scale balance and form of the symphony, something that many later 20C composers, more interested in small-scale movement (unless they're minimalists, whose large-scale is their small-scale written big) don't really try to grasp. As epic constructions, his symphonies really go somewhere. Simpson's problem for me is that I'm not always so convinced by the invention he uses to fill up these structures. Sometimes he seems strained and not as gifted as the masters he's emulating. But that may be my problem. I like Simpson best when he's openly channeling Bruckner's weight or Nielsen's rhythmic impulse, rewriting them in tougher mid 20C tonal harmonic language.

And from what I've heard of him doing it, Handley is highly attuned to Simpson's scale and language. So you could do well with this.