Sighting of a Little Egret pair

My question is how far north are Little Egrets supposed to have spread? I read that there are a suspected 200 breeding pairs in the UK but I have recently seen what looked like a possible breeding pair in and around the semi drained waterway in Hull Road Park, York. From reading about sightings this seems to be further north than expected.

Sorry no photographs because I was actually at the York Men's Shed building in the Park next to the drained waterway for our first possible full members (although outdoors) meeting in almost a year.