How to find stopcock if it's not under the sink?

Check if there is a small grid outside you front gate or driveway with a "w" on. Lift and should be a stop tap inside

Finding a mains stop cock tap can be a tiring task the best way is to trace back from a cold pipe you can see visible, in some cases the mains is installed at the front of the property i.e near the front door, area under the stair case or sometimes near a utility cabinet inside normally near a gas meter if still unable to trace the water mains tap inside property, every property has a point for isolation on the pavement outside the property whether it is a shared or individual tap.

yes as above they do have a tenancy to hide them mine was hidden in a cutout in the skirting board in the front bay window basically the other side of the wall where the mains water entered the property. happy hunting alex