Replacement exam certificates can only be obtained from individual exam boards. The cost of obtaining these certificates is individual to exam boards.
Please find below the contact details for the exam boards that we currently use:
http://www.aqa.org.uk/contact-us/past-results-and-lost-certificates
http://qualifications.pearson.com/en/support/Services/replacement-certificates.html
http://www.ocr.org.uk/i-want-to/lost-certificates/
http://www.wjec.co.uk/students/certificates/
https://www.gov.uk/replacement-exam-certificate/if-your-old-exam-board-no-longer-exists