Make sure you really think about this and discuss with some people first. No need to rush the decision. Wanting to quit is very common for he candidates, I wanted to several times.
Saying that, given your prior posts it is possibly the best idea. There is no point forcing your way onwards hating every moment. Things only get harder and more stressful as you progress in a phd. it is definitely better to free yourself now than continue with the suffering needlessly.
I don't know about the Uk so much but in most of the world there is at least a 30% attrition rate in the first year of a PHd, it is basically expected that at least 1/3rd of the people will drop out. Hck, I held write a rage funding proposal and when working out the finance numbers for phd that would be hired we incorporated a 35% drop out rate for the first year phd students.
I have known some very smart, very hard working and very nice people run to the hills screaming after 2-4 months, let alone 1 year. I nearly quit my phd at the end of the first year, my supervisor was horrendous, the project was flawed due to political issues, the work load was far more than I imagined ( and I was imagining 50-55 hours a week) , I also became massively disillusioned with science and academia. I hate a hellish time for nearly 5 years. 18 months since I finished and I am happy I persevered and the phd has been very useful to me already so I don't really know what to say to people considering thinking of doing one. Howver, I dropped academia instantly and I am far proffering working in industry. I currently do all the best bits of academic work- I research new solution to complex problems, read plenty of interesting papers, can write my own papers and patents, travel to related conferences, work with very smart people who are them selves ex-academics (profs from oxford, Stanford, MIT, phd grads from such places). The benefits are I work 40-50 hours a week not 60-70, I earn a large salary, I have far more freedom in what I do and my work style.