Wow, that's very unlucky. You did the right thing getting to the GP so quickly, and he absolutely did the right thing in getting you into hospital. Cellulitis kills and it kills quickly, from what I gather from
Mrs Big G, it is an infection of the tissue cells that causes them to die, and as they do so they release toxins into the blood stream that can cause scepticaemia...I think it is this that actually kills you.
You can also get it from infected insect bites, so if ever you have a bad bite that swells right up do the drawing rings with felt tip thing to see if it is spreading. If it does, especially if it tracks up veins etc, get thee to a quack quick smart.
Good to hear that all is well now tho