I recently moved into a property (in the UK) - it's a 1930's semi which was renovated about 2 years ago. I am wanting to have a water meter fitted - utilities company came to have a look and couldn't find a stopcock in the house. There is a mains stopcock in my front garden which controls the supply to both mine and adjoining neighbours, but nothing we could find in the house. I struggle to believe that i can't turn my water off without disturbing next door - is it a legal requirement or building regs requirement to have an individual stopcock in each property?
If it is a requirement to have independent control of the water supply now then it won't be applied retrospectively unless and until you have some work done on the water supply.
The first thing you should do is arrange with your neighbour a mutually convenient time to fit individual stop cocks. Then when this is done you can then arrange with the water company to fit the water meter.
Having said that, we have a house built in the 1890's that has it's own stop cock so it might be that you just haven't found it yet. Have you checked close to the house?
Another possibility is that the stop cock has been buried in a floor. This was the case in our previous house where the kitchen floor had been relaid and the stop cock - which was just below floor level inside the house - had been partially buried.