HM Courts Service provides information about debt recovery for small businesses. This shows that you don't need to use the services of a solicitor. Indeed, it specifically provides this warning:
"If you have a solicitor and your claim is for less than �5,000, you will usually have to pay for his or her help yourself, even if you win your case".
The information is quite comprehensive. It includes a specimen letter to send to the other party. There's also a phone number for obtaining further help. You can even issue your claim online:
http://www.hmcourts-service.gov.uk/infoabout/c laims/business/index.htm
Chris