Whenever I have had a GA it has taken a week to get over, whatever I do and however minor the surgery.
I feel fine and awake, and sometimes full of energy, then suddenly very tired and have to lie down immediately. Last time, I just gave up and paced myself accordingly and found out how olives are produced (amongst other useful information) on Ch 4 daytime tv.
Hope all goes well and you don't catch anything on the tube rides

(FWIW, I know someone who works in a London hospital and travels in every day and is still fine)