Get some quick dried yeast.

Late one evening, put a big spoonful of yeast in a bowl with a teaspoon of sugar and some wholemeal flour and mix with enough water to make it into a consistency similar to emulsion paint. I make roughly 500 mls of this mixture, but there's no need to measure it out, remember we're cheating here. Leave it for 24 hours. It should have gone all frothy.
Put half of it in a big bowl. We'll come back to that.
To the half that's left, add some more wholemeal flour and water to bring it back up to the same quantity, and again to the emulsion paint consistency. This is now your 'sourdough'. I keep mine in the fridge and only use it about once a week, but if you're going to keep it at room temperature or not use it for longer, it might be a good idea to feed it now and again by throwing half of it away and topping the remainder up with flour and water. Now you can forget about that for a while.
To make the bread, you now should have half of the original mixture in a big bowl, in an evening. Add a load of water*, a bit of sugar*, and a load of flour* and make it back up to that same emulsion paint consistency. Cover, and go to bed.
In the morning, after your first cuppa, give the mixture in the bowl a good stir (it might have gone a bit runny and should have bubbles in it), add some salt, add more flour and knead it. Shape it, or put it in tins or whatever (I use casserole bowls, and I use the lids when cooking because I like a soft crust). When it's risen, bake it in a hot oven, gas 5/450F/230C for 20 mins, then reduce to about gas 5/375F/190C until it's done (about another 20 mins).
Done.

*obviously, how much you use depends upon how much you want to make. I have been using about 27-28fl.oz. water, a teaspoon of sugar (which I don't think you need at all really, it's just a habit with me), and whatever flour I need. This gives me 3 loaves in my set of stacking casserole bowls which are all different sizes.