At any time after posting you can track your parcel using Royal Mails Track & Trace service.
When giffgaff return centre receives your parcel you will receive an email to confirm its receipt.
The returns centre will inspect for any damage or missing accessories. When these checks are complete, the return centre will let you know if your return is accepted. If your return is rejected (due to missing items or past the 14 days since booking your return), the parcel is automatically returned to the address listed within your giffgaff account.
You can track the progress up until this point by:
After returns centre inspect for any damage or missing accessories the finance team will start to process your refund. You will receive a e-mail from them once the refund has been processed. Please allow 5 working days for the refund to reach your bank account or credit card account.
Are you looking at the order history of the account you used to purchase the phone?
When was it returned / received by the returns centre?
Yes. I'm a bit concerned as the phone should have been received at the Repair Centre but it isn't yet recorded.
You're not the first to mention that returned phones have not been promptly recorded as arriving at the repaid centre. I can only guess they have a backlog.
Refunds are issued within 14 days of the phone being received at the return centre. Refunds to bank/credit cards generally take up to 5 days after the refund has been processed to arrive on the account.