The bikes are not free. Whenever did you find a transport solution (other than walking) in London for free? Ever? Public transport costs money to maintain so they’re making money out of people like you. Bikes really are £1 AS LONG AS YOU
KEEP UNDER 1/2 HOUR for each dock-to-dock journey. Cushty! You can do as many journeys as you like within 24 hours AS LONG AS EACH JOURNEY IS LESS THAN 1/2 HOUR.
The writing is on the wall, next to the bikes in fact. Note, if you want to do a journey longer than half an hour park the bike in a dock for 5 minutes and then you can get another one. It can be done
Have fun! Good luck!