Barmaid may know.
I don't know the legal position but I'd have thought as long as the position on his legal name (regardless of what he is known as) was clear to the court he would be addressed as/referred to, I imagine, Mr Stapleton/the defendant as a matter of court etiquette.
Not sure if they had given a silly or disrespectful etc... surname though - I doubt the Judge would let the court to or legal that legal representatives would indulge it - maybe it would be specified (or ordered as is, I believe, the case in proceedings where anonymity is preserved!) how they are to be referred to if an issue arises and any issues of reference to names he is known as cleared up as context would require throughout the proceedings such as in witness evidence.
I do wonder if they changed their name by deed poll so it was their legal name though!
Contempt of court could maybe come into play should disrespectful behaviour continue. From the news reports it sounds like they may be in for more issues with him, refusing to stand etc... Sadly though I don't imagine that is a rare thing in the criminal courts.
I'm interested to know the answer.