When I received my EE PAYG nano-SIMs, I tried to use one of them, but it said "Inactive SIM" on one phone and just a generic "No Service" message on my iPhone. I spoke to EE who said they were experiencing widespread problems with activation of the new PAYG SIM cards, and they would fix it within a day or two. I have just received an e-mail from EE, full of marketing-style HTML and images suggesting it is sent to large numbers of customers, saying:
We have been made aware of a problem when you tried to use your nano SIM card, which may have meant you were unable to top up and use it. Please accept our sincere apologies for the inconvenience this has caused you. The issue was due to a system error which has now been resolved. We will have your SIM up and working within 1-2 days and a £5 credit will be applied to say thank you for your patience. We hope you will enjoy your new EE SIM.
It's not clear whether the free credit will apply only to the one nano-SIM that I tried to use or whether it will also apply to the three other SIM cards that I ordered.