Yes you can still get the Apple TV offer free for 1 year, as this is through Apple and not O2 🙂
Open settings on your new iPhone and it will show ‘Apple TV+ Free Year Available. Click that option and accept the offer and input your payment details (this is only for when the free 1 year period has ended. You can cancel to avoid further costs) then you are good to go.
It’s worth nothing that the Apple TV must be accepted within 90 days of device activation