Take your time and look both at O2 direct and the independents.
That's if your not wanting a refresh tariff as only O2 direct can offer this.
Do you need a new handset. If not think about sim only contracts.
Do you want a contract or payg.
Make a short list of phones that tick your wants and needs boxes and then Go to the shops and have a play with working demo models.
Take your time and enjoy the journey.