I’m in the United States and am interested in applying to UK colleges, but I have not taken any AP tests. I’ve taken nearly all honor’s classes, and have also taken two college courses. Would that be enough to supplement my lack of AP scores? Would any schools be ok with this? I’m a pretty good student and my estimated ACT score is 29.
Definitely not. UK unis (with the marginal exception of St Andrews) will not look at your transcript (a few will ask for a GPA, but it will always be much lower than you are likely to have). Either sit some APs or SATIIs that are aligned with the subject you are applying to study (so if you want to study English, self-study Lit & Lang & sit them). Most unis will also accept SATIIs, but you will absolutely need 3 standardized test scores, and usually an ACT/SAT as well. Each uni has very specific rules that are outlined on the International pages; be sure to check the subject pages to see if there any specific courses required. If there are no specific courses required, make sure that at least 2 of your 3 are somehow similar (humanities for a humanities subject, sciences for a science subject). While you are at it, read the description of the course you are applying to very very carefully- they are typically much more prescriptive than in the US.
Also be aware that any admission is likely to be conditional. This is not a US applicant thing. Almost all British applicants also receive conditional acceptances. This is because students in the UK take their A-level exams at the end of their last year in secondary school, and the universities will not have the scores yet when they make admissions decisions. So if you are applying to read (say) Physics, they may require 3 AP exams including one in Physics and one in Maths with scores of X. Or they may say that you need at least 3 SAT II tests, with a minimum score of 700 in Physics. Your mileage will vary with your university, but expect any offer to be contingent on future performance on some exam.
Test scores are king in the UK. Even St Andrews–which is the most familiar with the US–requires some form of standardized examination.
When I was applying I did find, however, that they did not necessarily require 5 “5s”. Not even Cambridge. They will look however for evidence that you are prepared for the course.