How to turn the water supply off from the street ?

Section62

NSG666 said:

...or, if it's like Section has said, modify the access chamber all at no cost to you if it's not on your property.

I guess it is possible the chamber has already been modified with a slot cut in the side to give access to the valve, but we can't see it because the white cap is in the way.

Here's a couple of examples of meters from the same manufacturer showing the position of the valve on their base unit, and the shape and size of the chamber for comparison.

Another_Level

Hopefully the OP has sorted it out  Their water supply company should be helpfull with advice 

Sometimes when there is no stop valve, the actual water meter is designed to be rotated 90 degree to isolate the water supply, severn trent water had some of those type water meters for a while.

They can be turned by hand, its awkward or an appropriate meter head key will makes it easier