Street water stop tap uk
I think it should be fine to use the one outside to shut off your water.  It is recommended to use the inside stop valve but if that is broken or if the leak is in the section of pipe between the outside valve and the inside one you can use the outside valve.  Also check that your outside valve isn't shared with a neighbour which is sometimes the case.
At least in my area the water company provides instructions on how to use the outside stop valve, see https://www.thameswater.co.uk/help/emergencies/how-to-turn-your-water-on-and-off/how-to-find-and-use-your-outside-stop-valve .