Being offered by
https://thepeoplesoperator.com/get-free-simWho are an mvno that piggy backs on EE.
Offer T&C are :
"The standard PAYG SIM will come with instructions as how it should be activated.
The offer is only available to non-customers of TPO.
Only one SIM is permitted per user.
Only two SIMs are permitted per household.
The SIM card will only work if placed inside an unlocked phone.
By registering, you are giving TPO permission to contact you.
This offer is available for a limited time, and The People’s Operator reserves the right to withdraw the offer at any time."
Handy to put in a spare phone.
Their rates etc are here:
http://www.thepeoplesoperator.com/pay-as-you-go