May has not really added anything new to PA policy, I feel. The austerity policies of the coalition government headed by Cameron also added nothing new but austerity has deepened the marketisation policies of the Thatcher era. All governments since the earrly 90s including New Labour have really been pushing for new public managment policies. So, any apparent changes have been in style not substance.
In my opinion, the name of Prime Minister May will be associated in history with the Brexit and I think that this is unjust. The macho-populist front-runners of the Brexit campaign proved to be unbelievable coward in taking responsibility.