"Have a drink at the pub just by the Tate. If you've got an hour to eat, have the smoked salmon platter - delicious! OK it's not 100% free, but you can go there on a break from all these free things :)"
"Go to St. Paul's cathedral, walk on Millenium Bridge and"
"So many things to say! So many things to SEE. Picasso, Monnet, Anish Kapoor & more. 3rd level worth seeing if you don't have much time on your hands. While you're there see the next 2 things below..."
"Brilliant gallery - just go and see it! On your way in/out stop for a moment in Trafalgar square, a popular meeting point."