Percy Grainger, like Ralph (pronounced Rafe) Vaughn Williams was a composer in the "classical tradition". Like Vaughn Williams, he used folk music as an inspiration for various works, often using the melody from a folk song as the starting point.
He was born in Australia. Grainger, along with Cecil Sharpe and others, was one of the late Victorian/ early Edwardian fok song collectors - some info about him HERE
I am not a great listener to orchestral music, so can't say how close his work is to the original tunes.

As for using brass band arrangements with other instruments. If you are using, for instance, Bb brass insruments and clarinets in Bb there isn't a problem. The clarinet is working in basically the same range as the cornet parts. During time at school I played with a mixed wind band where cornets and clarinets shared the same music.
If you were using instruments in different keys. Bb cornet and C natural trumpet or flute (or wooden flute in D), you would have the problem of transposing parts so that all instruments fitted together.

Here's a link to try a search within The Music Room (Not the folkie shop in Cleckheton)
Quack!
GtD.