Get 20% off payg mobile phone top ups at Tesco instore.
The sign said you need to go to the telecoms dept. but we didn't have a problem getting the discounted top up from the tabacconist section.
If you are with o2 don't forget to register for rewards, surprises and treats.
My 'surprise' for topping up with £10 was 20 free texts, a nice little bonus!