Leighe,
About PS's...you just never can be sure. You could show up and see a few empty tables or, like when we were there in early December, there could be thirty people waiting standby--none of which were ever seated. All the people with PS's showed up. I really think that the tea is gaining in popularity. I wouldn't chance it. Unless you are staying at the GF so going by there wouldn't be out of your way...
I loved the tea sandwiches that came with my order (Buckingham Palace, maybe? I'm not sure now...)! If you have the opportunity to have a chocolate dipped strawberry, do! I didn't order the tea that is the house specialty. I ordered a cinnamon one that was truly wonderful. (Someone else on this board suggested it.) I'm usually a chocolate nut, but my server steered me away from the chocolate finger cake I was going to select and toward a puff pastry swan filled with a sweet cream. It was to die for! Make sure you try it!