If you are both British subjects and wish to get married abroad, you may still need to give notice of marriage in the district where you live.
Please note that your notice is posted for 28 clear days for the purpose of objection. So if notice is given on the 1st of the month, then the certificates would not be issued until the 30th.
The registrar will issue you with the appropriate paperwork, known as a 'certificate of no impediment to marry'. This will be required in the country where the marriage will take place. It has no expiry date, but you may find it is not accepted by some countries if it is dated more than three months prior to the ceremony. Please check with the relevant embassy to confirm their requirements.
You will also need to provide the registrar with the name of the town or location where the wedding is to take place, as well as the country.