Yes Ian my impression too - although the RSPB guys are apparently still divided. Did Father Ted say "how big is that cow"? i.e. without something to compare size a cow in the distance can seem quite small as in this case was the Egret as it was on the border pool and viewed from the top meadow.
Black bill and black legs sounds more akin to Little Egret I'm afraid. The colour of the bare skin of the lores might have helped if you noted it but size is often very difficult to assess subjectively without direct comparrison to another species.
Yesterday afternoon my wife and I took ourselves over to Burton Marsh - parked the car at the bottom of Station Road/Denhall Lane just past the reserve entrance near to the new entrance to the Burton Point walk. When we got back some kind person had decided to have a look if there was anything of value in the car by breaking the rear window. Luckily I had taken our scope with us as an afterthought. So if visiting this normally pleasant area it goes without saying don't leave anything of value in the car and/or park on the reserve and walk down.
Subsequently visited Inner Marsh and found 4 Spotted Redshank in stunning summer plummage, the Green Winged Teal, common Tern and a possible Great White Egret that became the subject of debate amongst the assembled group - Big white bird, long neck, long legs, black bill, black bill?. Understand that Great Whites get a black bill at this time of year - does this happen to only the males does anyone know?