Correct, we just need a photocopy of BA diploma including Apostille stamp on it. Original Diploma is not necessary. However you need to obtain Apostille on the original copy of CBC.
You would want to get a copy of your BA diploma apostilled. To get your diploma apostilled, I will provide you a link for more info: https://www.korvia.com/apostille-korvia-guide/
You will have to notarized and apostille your PGCE since it will be same as your BA Diploma and instead of TEFL certi, you will have to send photocopy of your teaching certification that is not apostilled.