If you look at your resevation online on the day of arrival, you will see if the room allocation fairy has given you an upgrade.

Most times that is then what you get at check in, although at times, I've had a further upgrade allocated manually when I arrived.

An example at Chancery Court last week where on the day of arrival, the website said I had a clubroon floor, but on checking in, I was allocated a suite with the printed club room number crossed out and written over in pen on the registration card.

An email 48 hours before arrival may help the initial room allocation, and then it's down to charm and luck to see if you can get more at check-in.