If your business is located in UK and you want to outsource your work, you best choice should be UK based call centers. If you want cost effective call centers you may find call centers in Pakistan and India.

Following are some web directories listing UK and international call centers.
• Company Seek
   http://www.companyseek.com

• Knowledgestorm UK
   http://www.knowledgestorm.co.uk

• TelePlaza
   http://www.teleplaza.com

These are popular web resources; we hope you will be able to find best call centers.
Before choosing any call center consider the following tips:

• The call center you are hiring must provide its service in the language that your customers speak.
• It must be cost effective

Conclusion:
If your business is located in UK and want to hire a call center, your best choice may be UK based call centers.