Unless there is an in-universe source which spells his surname "Atlee", the page should use the real world spelling of "Attlee".
Talk about it here.
Clement Atlee was the Deputy Prime Minister of the United Kingdom during the Second World War. In 1941, Winston Churchill asked for a message to be sent to Atlee to arrange a War Cabinet meeting to discuss the Dalek threat. (TV: Victory of the Daleks)