I feel that June is too soon. It's putting a lot of pressure on us all to make decisions, and it's possible that some readers haven't even had a chance to see the thread yet.
As far as having less to do in September, I don't think that would be too much of a problem. Although people coming from across the ocean do like to sightsee every day, not everyone does, and if it's a lovely location, just walks are outings, fresh air and sea air can make up for places to go? The local towns are cute to see aren't they? Cambridge is stunning, London is a train ride away if someone wants to go for the day. I'm sure there are other things, too. Aren't there lovely old English cheese villages around there, Treasur? I don't know why but cheese comes to my mind. And pretty Miss Marple villages with tea rooms and antique shops? I seem to remember that.