I was prescribed diazepam about a month ago for severe anxiety to the point of being suicidal. I was prescribed 2 to 4mg, 2x daily and given 14 tablets. So far I've only needed 3 doses to get my anxiety under control and keep it there. The first two doses were within 24 hours and the third dose was about a week later. I was a bit drowsy each time, I was relieved to get some sleep and just being out of it helped a lot. I did notice the third time that my mood dropped significantly, benzos aren't really ideal when suffering from depression but if you are so anxious that you are not safe then it is a trade off that is probably worth making. As you are in the UK, you were probably only prescribed a few low dose pills, like I was, so the risk of addiction is kept to a minimum.