Sorry Studentgal, you are wrong I'm afraid. Although a complainant can inform the police that they no longer wish to pursue the complaint, it is actually up to the CPS whether or not they wish to prceed with a prosection. The CPS have a set of guidelines which they must follow which include deciding whether it is in the public interest to pursue the matter and the likelihood of conviction.
If the CPS are continuing with the case despite you informing the police you no longer wish to proceed then they must feel that they have a good chance of a conviction or that the offence is serious enough that it is in the public interest to continue (say for public safety for example).
If the OP does not attend court then as a witness summons has been served then they can be arrested and taken to court by force. If they fail to give evidence whilst at court then they can be held in contempt of court and, if necessary, ultimately imprisoned for that offence.