There are two ways of getting compensation. Firstly the court could make an award or you might be able to claim under the CICA scheme:
http://www.cica.gov.uk/
Under the CICA scheme it's not necessary for anyone to be convicted in order for a victim to receive compensation. However the scheme calculates a compensation figure (according to standard formulae) and only pays out if the figure arrived at exceeds £1000. (If the calculated sum comes to less than £1000, as it probably would, you'd receive nothing).
A court can't order anyone to pay compensation unless they've been convicted of an offence. Neither you nor the police are 'pressing charges'. It's the Crown Prosecution Service which has brought the charges. If you failed to attend the court, your evidence couldn't be challenged by the defendants, so any statement you've made would be inadmissible before the court. Unless the CPS have got solid additional evidence (such as clear CCTV images) they'd have no option other than to ask the court to dismiss the charges.
If you receive a witness summons to attend court, and fail to do so, you'll be committing a criminal offence. In most cases nothing comes of this but you should be aware of the possibility of prosecution if you fail to show up.
Chris