Your stopcock should be below the kitchen sink on the pipework leading to the cold tap. In many houses the stopcock is fitted under the stairs. If your house has had the kitchen moved in the past then the stopcock may not have been refitted. Many homes do not have a stopcock fitted due to building work and neglecting to fit the stopcock valve back in a position that is accessible. Below is an image of a stopcock in-situ.
It has a chain so it must connect on where the old chain is...
Frantic emergency callout to a house with water coming from the ceiling of a bungalow in Harold's Cross. The three quarter inch qual-pex pipe in the ceiling above the boiler had, blown totally out of its connection. A lot of water was present in the house and the householders had been away on holiday. The pipe had disappeared up into the attic space as can be seen in the picture below. Luckily there was an emergency plumber on hand to rectify the situation at 3am.
Emergency callout to a house with water coming from underneath the kitchen sink. The rubber hose to the monobloc tap had burst, I capped off the pipes and stopped the leak. These hoses seem very prone to bursting as i often get callouts and, the tap hose is the culprit. Although the hoses do make connecting the tap up a lot easier than the metric copper pipe on other models.
Emergency callout to a house with water coming from ceilings at high speed. Narrowed down the problem to this wall(pictured) and cut an inspection hole. The elbow had popped off completely from the qual-pex pipe. The damage was not great as i got there quickly. Had this happened when nobody was home the ceilings would have come down and the damage and cost would be high.