Mine started to leak in my cellar, as I had to turn it off to change a kitchen tap, then there after it developed a leak and I had to use a bucket to collect the drips which would almost fill half a bucket in 24hrs!
I managed to temporarily stop these drips by wrapping the whole reel of PTFE tape around the stem and the body, it did the job, except now you could not turn it off if you had to as it got really sealed tight. But in worst case scenario, you would cut it off with a knife if you had to shut your supply down.
There is a service stop cock in the street but it is far too deep and I didn't have the right key for turning it off, a plumber would charge for coming over to shut it down!
But i noticed that every so often Thames water engineers with reflective yellow jackets would shut the hole street around 2am to keep their mains service valves from freezing! so they regularly stop the water and open again a few minutes later!
So what i did was bought a new stop cock, and had my spanners ready the next time I notice the water had been shut, so one night around 2am, that happened, and I rushed straight into my cellar, undid the old stop cock and quickly replaced it with a new one, everything went smoothly and a few minutes later the supply was back, and no more leak.
Obviously you need a bit of luck to do this, as there is no way you would know if they were there, so it is a chance thing. I remember i had gone to the toilet and tried using the water and it was dead, so I knew the water supply had been turned down that night!