Those who've read many of my posts on this site will know that I'm not a great fan of the police but, to be fair to them, they're always faced with a difficult task when it's 'one word against another'. If they simply ignored accusations of assault (because there were no independent witnesses) they'd be heavily criticised. They, together with the Crown Prosecution Service, seem to have taken the view that it would be best to leave it up to a court to decide whether there's sufficient evidence for a successful prosecution.
However your assumption that you can't use the services of a solicitor (other than the court solicitor) is completely wrong. If, as you say, you're 'totally penniless', you're entitled to (free) legal aid in respect of any charge which might (even if only theoretically) lead to imprisonment. Phone Community Legal Advice, on 0845 345 4 345, to be put in touch with a solicitor who can represent you in court.
Chris