The EU PlayStation Network will be going down for scheduled maintainance frm 4.00 PM BST July 26 to 8.00 AM BST July 27. The outage will affect the PS Store, account management and registration, but if you’re signed in before it happens, online gaming might be possible.
You can find more details about the maintainance on the official EU PS Blog. It isn’t revealed if the maintainance will affect the U.S and other regions.