Giffgaff is an MVNO on O2 in the United Kingdom and is a wholly owned subsidiary of Telefonica, as is O2 itself. If you order a free SIM card from
this link, you and I will both receive £5 free credit. You can even request delivery to your temporary accommodation; UK postal addresses are flexible and don't require the recipient's name to be displayed on the letterbox.
If you don't have a UK address, then please PM me and I will use some of my £5 free credit to cover the international postage to send a SIM card to you. You will still receive your £5 free credit as well.
You will need to top up your account with £10 in order to activate the SIM card. This can be done by credit card online or with a voucher from an O2 UK shop.