Wow, there are so many of us transferring out of Kent, especially Psychology!
My girlfriend goes to Sussex, and I held an offer from them also, so I've spent quite a lot of time there. Campus wise, it's quite nice although the buildings seem very plain. The Psych department is held in pretty decent esteem, they produce some decent research. The main thing I dislike, however, is the campus' lack of.. well, anything. There are like two bars, both are pretty grimey and one of which plays sports on uber volume 24/7. The campus cannot compare to what we have here at Kent.
Surrey, I also held an offer from. When I visited on an open day I was hideously put off. One of the grimiest campuses I have ever seen in my life. Our introductory lecture was in some dingey run down lecture theatre which was covered in graffitti. Horrid campus. Needless to say I turned down their offer.
But overall, out of the two, Sussex definetly.