Edit: After 11 hours there is still no sign of fermentation. Does chlorinated water kill the yeast? Surely not, or bread-making wouldn't work, particularly when you let the yeast grow in warm water before mixing it with the flour.
Our airing cupboard isn't very warm though. We have an extra insulating blanket over the hot water cylinder, and only have the hot water heater on at certain, crucial, times of the day.
Edit2: After about 31 hours or so, some fermentation is in evidence. I tried making the top receipe, but boiled the ginger dry. I went ahead and finished the receipe, but at the end it was too sweet and not gingery enough. I'll give it another go.