I think that most British Employers look at the highest level qualification as their main measure of educational achievment and won't be too bothered about understanding the lower levels - but they may be interested to know which subjects you studied in your advanced placement courses.
If you were applying to me (and, yes, I am British and have been responsible for selecting staff here in the UK) I would find your CV most positive if it stated something like:
Batchelor of Arts Degree in Ancient Spanish History from the University of Birmingham, Alabama, USA, 1996 - 1999. Equivalent to BA degree in the UK; see attached independent (NARIC) report.
In order to qualify for the Batchelor of Arts program, I studied Spanish, History, Mathematics and Economics in my final high school year; in prior years my studies were in History, Geography, Mathematics, English, Spanish, Physics and Chemistry, and I got "Grade A's" in all of them. There is no exact equivalent comparision to GCSEs and A levels in the UK, as explained by the NARIC report.
With - of course - all your details correct and not my fictitious ones, and the NARIC report attached stating clearly who NARIC are.