EE claims this charge is to "support investment", what a bunch of crap. They are just trying to get away with it.
Their sudden about face to charge an EU roaming charge will only last if EE's UK competitors don't charge the same or a similar EU roaming charge, then you will see another about face from EE with some type of "we are so sorry" mea culpa.
There are 4 big operators in the UK.
O2 and EE have both announced the reintroduction of roaming charges.