Find accountant for non-audited accounts

We are a small Limited company that meets the criteria for being able to file unaudited accounts. Company House now allows eligible companies to file the key figures for unaudited accounts online and will send a copy to HMRC for corporation tax. 

We never need credit or have any other need to present audited accounts to a third party, so our only obligation is to Company House and HMRC. We want to find an accountant that would prepare unaudited accounts from our Sage system appropriate for submitting to Company House and for HMRC corporation tax. The company turnover is £500,000 in a service industry and we have 2 members of staff. What would a realistic cost be for producing unaudited accounts and where would we find an accountant?