more than likely it will go trough on tuesday, but keep an eye on the signal from monday just in case. back up anything u have saved on the giffgaff sim because once the sim gets disconnected it's all lost.
You usually receive an email or text giving you a port in date, but you may not receive this until Monday. Keep an eye out for it but if not received CS can tell you from the notes on your account.
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.