Cid
Proper break this time
If you signal left to make the turn, the driver should expect you to slow to make the turn. They might hopefully spot the pedestrian and know you are going to stop but at least they know that you are about to do something.
I wouldn't expect any driver to know any of those group cycling hand signals.
The 'slow down' one is actually in the highway code for motorbikes/cars without signals. But 99% of drivers will have forgotten that regardless.