Well, you've certainly got me confused!
Firstly, I assume that you mean the Crown Court, rather than the County Court. (County Courts only deal with civil law matters. Crown Courts handle criminal cases).
Then you've said the charge is 'Common Assault'. That's normally a 'summary only' offence, which means that it can only be heard in a Magistrates Court, not in a Crown Court. ('Common Assault' can only be dealt with by a Crown Court if the defendant is also charged with a more serious 'indictable' offence at the same time).
Then you've said that the cost 'will be in four figures'. While that's probably true (if the case really is, for some unexplained reason, to be dealt with before a Crown Court), it's not necessarily true that your friend should have to pay it. Everyone who is accused of an offence which could possibly lead to a prison sentence (even if, in reality, such a sentence is unlikely) is, if their financial circumstances meet the relevant criteria, eligible for free legal aid. Your friend should phone Community Legal Advice on 0845 345 4345, to be put in touch with a solicitor who works within the Legal Aid Scheme. (He should get the solicitor to check what charge he's actually facing. If the matter has been referred to the Crown Court, it sounds more like the lower level of 'ABH', rather than 'Common Assault', to me).
Chris