I would, however, recommend Crystal Palace Park for any day, sick or not. It has some wonderful treasures dotted about it, including dinosaurs, a maze, some sphinx's, something that would seem to be a small Eiffel Tower, and some stunning examples of Modernist architecture. All in all, it's a surprisingly cultural day out, what with the remains of the Crystal Palace.
Enjoy the photos. And do excuse the casual clothes, I was sick.