From the gov site
http://www.direct.gov.uk/en/Governmentcitizensandrights/Registeringlifeevents/Familyhistoryandresearch/Birthmarriageanddeathcertificates/DG_175628How much will it cost to order by post or phone?
Standard Service
If you supply the certificate index reference, the certificate is sent within four working days. Without the reference, it will be sent within 15 working days.
* short certificate (birth only), with index reference supplied – £8.50
* short certificate (birth only), without index reference supplied - £11.50
* full certificate, with index reference supplied - £8.50
* full certificate, without index reference supplied - £11.50So with the index reference (which you have) £8.50.
Last time I ordered from a local office I had to supply a stamped, addressed, envelope.