Is Tesco Mobile GSM or CDMA UK and Can I buy an iPhone 5s with it UK?

Is tesco gsm or CDMA an can I buy it with an official unlocked iphone at apple store Westfield uk

CDMA is in the main the USA
CDMA phone do NOT have a sim card slots the phone is activated by the network

There are NO CDMA networks Europe! It is 100% GSM ie simcard so unlocked phones and local sim card for travellers.

From the IP4S onwards iPhones are what is know as "World Phones" having BOTH GSM & CDMA functionality

So if Apple store Westfield UK has the IP5S and you decide to the US as in A, ( NOT US being me and my family showing off you new phone NO way will that be tolerated) you can with an unlocked IP5S use any of the US networks either GSM or CDMA