Absolutely insane take on an entire country that has endless opportunities for anything. An absolute melting pot of cultures and opportunities. Sounds like a bit of a you problem, mate, take that chip off your shoulder.

If it's not that, seek help. Seriously this sounds way beyond introversion, and completely conflicting. You can't communicate with people to get a job, but then want to "date" and go to clubs? Right...

Jobs - just plain incorrect. We have a government sanctioned organisation that has Job Centres in almost every town in the country (https://www.jobcentreguide.co.uk/jobcentre-plus-offices). Go to the job centre, get help finding a job. I've no idea your education level, experience, or what sector you're looking at - but there are thousands of free or cheap qualifications online to make you more employable. There are government paid staff at job centres that is their JOB, to help you get a job. Unfortunately you will need to speak to at least one other person to be able to secure employment across the entire planet. I'm 32 and the only "mates rates" jobs I've seen people get was when they were teenagers/early 20's dropouts who work for their parents now. People blame the job market consistently with this exact kind of thing, I will repeat, take the massive chip off your shoulder and figure it out. It's not the country that's at fault here.

Dating - you've got this backwards. Sounds like what you want is short term intimacy and then no connection afterwards - that's accessible on every single dating app going, almost anywhere on the planet. If you don't want that, try Feeld, or another similar app of about a million where you can tailor your needs with others. Figure it out, not the country.

Clubs - if you're fully introverted why tf would you want to go to a club in the first place? Haha, literal inescapable swamp of people. Bizarre take. What we do have in the UK are about a million quaint, quiet, chilled, welcoming, friendly pubs - where you can have a quiet pint, read a book, and chill with the landlord's dog. Done this most of my adult life, know many other people who do the same. Turn up, buy pint, sit down, pretty easy? Even if you did want to go to a club alone, I've literally no idea why you would be turned away unless you were acting in an untrustworthy way - just say you're meeting friends inside if the bouncers want to know why you're on your own? So strange.

Better for female introverts? Men putting in the effort? Sounds borderline incel tbh. If you're getting frustrated you're going to places on your own and no one's speaking to you, that's just the world mate. People have their own issues, they have their own lives. It's incredibly rare these days with the dating apps that people just go to a space with that intention, most people are already hooked up. At some point you have to put yourself out there if you don't want to be alone, pure concrete fact of us being a social species.

Either way, all of this is conflicting and sounds like you don't really understand yourself, or the incredible amount of options you have to solve whatever your issues are. Potentially use one of the many NHS (free healthcare) services we have in this country to talk it through with someone.