O2 priority, have a really good loyalty scheme for people who use their mobile phone network. It gives you things like the £5 Pizza Express pizzas and the Caffe Nero free drinks when available. If you’re not with O2 then beg or borrow an old smartphone and buy a £10 pay as you go O2 sim card to get O2 Priority. Send a text every 6 months to keep the sim live and enjoy all the benefits of O2 priority for not much.
Keep your mobile data switched off to avoid using the credit and use your home wifi or The Cloud free wifi if you’re out and about to get the codes.