Sorry forgot all about this.
No issue with drainage IMO. Your concrete has just cracked. There are multiple slabs that have been cast at different times, with no expansion joins / construction joints. If it was my guess, you sub base has settled a few mm and cracked the concrete. Also the combined actions of the weather will have caused it to crack and water can seep into your sub base causing settlement. Concrete, no matter how well its laid will crack over time. Rip it up, make sure you spec a good sub base (200mm MOT 1 or such) making sure its properly compacted, the put a new finish on top. I really dont thing you will have any problems *
* all based on pics, dont sue me when your house falls down.