With music notation software now being readily available, more and more brass band musicians are turning their hands to arranging music for their band - and doing a very good job of it too!
As you should be aware, in the UK, copyright exists on any piece of music whose composer has not been deceased for over 70 years. Any arrangement of music, still in copyright, MUST have permission from the copyright holders, otherwise the arrangement is illegal and the copyright holders can take legal action against you.
Even if your arrangement is not for profit, not for public performance, not for sale or only for private performance, the copyright holders must still license the arrangement.