You probably don’t recall, but it is usual that statements taken by the police conclude with words to the effect “…I am willing to attend court to support a prosecution if necessary”. Anyway, no matter.
The CPS have a Witness Care section. They should be in touch with you and you should speak to them to share your concerns. A bit of info about their roles and responsibilities here:
http://www.cps.gov.uk/news/fact_sheets/witness_care_units/index.html
Before the trial (if the matter gets that far) they will hand your details- including any concerns you may have - to the Witness Support Service at the court. They are part of Victim Support and they will support you through the court process and can arrange for you to visit the court before trial day to familiarise yourself with the surroundings. They are expert at dealing with nervous or anxious witnesses and you will be by no means the first person they have encountered with your worries. You can find out a bit more about what they can do for you here:
http://www.victimsupport.org.uk/help-for-witnesses
Lastly, you have done the right thing by making a statement and you should be prepared to follow this through if necessary by attending court. Without witnesses being willing to give evidence there is no justice and miserable toe rags get away with all sorts. You can do your bit to reduce that.