Legit Second hand phones shops online?

My daughter would like a new phone for christmas and said she would prefer a second hand one as is much much cheaper! Does anyone know any good legit online second hand phone shops? We're in the UK and would be looking to get an iPhone 7. I have looked on 4Gadgets but is out of stock there.
Also does anyone know if second-handphones.com is legit?

CEX are really good, and all goods they supply come with a free two year warranty.

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  • Is my new iPhone second hand/refurbished? Logged onto McDonald's Wi-Fi with my brand new phone and someone else's name was registered. How is this possible? When logging on phone said welcome back chrissie someone or other with a Not You? Option