Re: reasonable person?
Wouldn't that depend entirely on where in England the case took place. I believe there a cities where the "ethnic minorities" are only minorities when compared to the entire country but locally represent a very large part of the society. Therefore it is entirely possible, and not misplaced, to have a jury made up from 12 people who consider not wearing a headscarf a crime.
Even if the jury were made up of 12 such individuals, it would not make any difference.
A 'reasonable person' (aka 'the man on the Clapham omnibus') is not a juror, but rather a legal fiction used by the court as an objective test. This legal fiction, in essence, represents your average citizen and not the jury. Therefore, even with such a jury, it would be a non-issue in a UK court of law.
Quick example, different area of law, but the principle still holds: http://www.lawteacher.net/lecture-notes/tort-law/negligence-breach-lecture.php