The CAA has a dedicated online application page for Standard Permission to Operate Unmanned Systems in UK Airspace
You can apply for your OA using the CAA's online application portal only for Standard Permissions to Operate Unmanned Systems in UK Airspace.
Make sure you note down the tracking number on the top right hand corner of the screen and if you are having difficulties with the system, please contact a member of the SSC UAS team as soon as possible, by phone on 0330 022 1908, or by e-mail at UAVenquiries@caa.co.ukbetween the hours of 09:30 and 15:00 Monday to Friday.
Don't forget, for new applications you will need your GVC Certificate, your Operations Manual and your Insurance.