In a previous post I drew your attention to the free online Saylor Academy Sociology 101: Introduction to Sociology course and you might be interested to know (or know a colleague who is) there’s also a free online Psychology 101: Introduction to Psychology course available.
Although, as with the Sociology course, it’s aimed at American Community College students – and the various credits and certifications available for completing the course will only be meaningful and useful to US students – this doesn’t mean that actually completing the course won’t help UK a-level students because the overall level is broadly in line with a-level studies. A quick look through the equally-free Open-Stax course textbook that accompanies the course should confirm this for you.
Alternatively, have a quick trawl through the course syllabus that covers a number of Units that should be broadly familiar to a-level teachers (although whether the actual content is the same / similar is something you’ll need to check):
In addition to “read stuff from the textbook, think about it, make some notes and maybe answer some online comprehension questions” there are a number of other resources (such as PowerPoints and short Video Tutorials) liberally spread throughout the Units that might be useful even if you don’t want to go the whole hog with the online course.