As I'm not a complete idiot, I started off riding on the quiet residential roads near to my house. The level of traffic is ~1 fairly slow-moving car every 3 minutes, which isn't too bad. I achieved my trip to Sainsbury's quite early on - mostly it took time because the roads round here are a bit non-Euclidean (you think they're straight roads at 90 degrees to each other, but suddenly you end up in a road parallel to the one you started in). Of course, I didn't attempt to ride across the busy main road where Sainsbury's is - I got off and walked across at the pedestrian crossing. Later, I went down to the river - walking some of the way because a hill was involved - and rode around in the park for a bit. The biggest problem I have is that the cambers in the roads are in the "wrong" direction for me (my left leg is much weaker than my right, and the roads slope to the left so that rain runs into the gutters).
I then attempted to get into Kingston town centre, and found it a bit harder. All the cycle paths that go round the town centre are along the main roads, which is barely much safer than cycling on the actual road. Going through Kingston is difficult, because most of it's pedestrianised (walking humans only), and the rest of the roads are mainly inhabited by buses - of the large, red, double-decker type. I'm not even going to attempt any of that without an instructor.
So I've been trying to find a provider of specialist cyclist training. The council runs cycling proficiency courses for adults, but the next one doesn't start until 10th August. They also do individual training, but I don't know how much it costs or what the waiting list is like (I've emailed to ask). I specifically want training to teach me how to cycle on roads with moderate levels of traffic, which means off-road training isn't much use. There seem to be two possibilities: the London School of Cycling and Cycle Training UK. The former has a web site that severely hurts my eyes (white text on tomato red background? with navy links?!), while the latter charges £27.50 per hour for individual lessons, which is a) more than I charge for science tution, and b) more than it costs for car driving lessons.
I'm going to look into this further and book some lessons, but after that I'm wondering whether anyone who regularly cycles would like to come and keep me company as I wobble around SW London. I have no idea what kind of distance I could expect to be able to manage, but I'm hoping I'll be able to learn how to deal with hills fairly quickly so I can go to Richmond Park.
And in case you're wondering, I'm still ill and not able to eat much of my normal diet, and needing a lot of sleep. But I'm bored rigid with sitting around at home, I stopped being ill enough to faint or vomit after the second day, and I have a phone with me anyway. Just in case you were worried ;)