Between Brexit and COVID most of the typical destinations are out for a while, by the sound of it.
Almost all of the people I knew who did gap years before or after university went to either Australia or New Zealand (from the UK) following a three teaching-year degree with an extra industrial placement year - Australia in particular have (had?) a scheme where someone can live and work for a year with few restrictions provided they are under 30, and could extend that to two years if working in a rural area for some of that time.
It's called the working holiday visa. I went to New Zealand on that after my first job. You have to work in agriculture for 3 months to extend your one year visa.
Almost all of the people I knew who did gap years before or after university went to either Australia or New Zealand (from the UK) following a three teaching-year degree with an extra industrial placement year - Australia in particular have (had?) a scheme where someone can live and work for a year with few restrictions provided they are under 30, and could extend that to two years if working in a rural area for some of that time.