US iPhone 5S & SIM

[Tomsk]

My US cousin is coming over to the UK for a couple of weeks with his iPhone 5S.

AFAIK the 5S is compatible with UK networks, right?

Also he wants data and to be able to phone home. Can anyone recommend a SIM? I'm thinking 3 or GiffGaff.

 

[Tomsk]

He's asked about getting a new card (SIM) so I presume he has the GSM compatible version.
I'll check with him.

 

[Tomsk]

According to this

https://www.apple.com/iphone-5s/specs/

They are all GSM capable.