As an over 18, employing you as an apprentice will cost employers more. It's not as simple as saying "I'll just get an apprenticeship". Do you have any paid work experience? For the jobs you are considering, paid experience working with members of the public will look great on your CV- could you organise a summer job or weekend job this year? Unpaid experience is good too, but most employers will value paid experience more, even if it's not so directly related to the job.
Most employers do value experience, but it doesn't sound like you have any, right now. For some levels of work, you will be expected to have a degree, so you may have to start off lower down the ladder than you would like. It depends what you class as a "decent job", many people can't get well paying work even with a degree, or years of experience or both.
However, it might be worth spending a year or so exploring your options after sixth form, and if things don't work out, you can always go to uni later. I do think if you want a "career" rather than a job, going to university will probably help. If you don't like psychology, what about something else e.g. business related or marketing?