Agreed with everyone else, this is an amazing first orchestral piece! Absolutely love the composition and general theme of it, and it really fits the theme. And the variety and scale of it is truly awesome!
I do agree with some of the comments about the transitions, especially the cutoff around ~3:40. And if you're looking for some BBC Symphony alternatives/additions that lets you play with attack and release, Orchestools is another free one that you can mix in with the BBC instruments too add some extra layers which can help with that sometimes.