I'm not sure where you're based, but there are lots of providers for public (rather than workplace) first aid courses.
eg (Scotland focused): https://www.firstaid.org.uk/course_cate ... d-courses/
Most courses are based on this book: https://www.amazon.co.uk/First-Aid-Manu ... 241241235/
(many other suppliers, many cheaper, are available) which I'd strongly recommend getting. Its probably too detailed - you may well get a bit lost - until you've got some familiarity but good to brush up on from time to time.
There isn't really an audit process for courses - so do look for local recommendations.
The last first aid in the workplace course I went on, from one of the national providers, was pretty poor. For some people on it, it was a refresher for which it may have just about been adequate, but for some on there, for which it was a first course, it missed some of the basics. Lets just say I gave A LOT of feedback to them afterwards.
I will say, I know people who have been on courses but who aren't comfy at all at doing anything, and whose brain will go blank in a real incident, so don't hesitate to call 999 and follow the call taker's advice and guidance. No two incidents are identical, so much of first aid is really enhancing your knowledge and providing tools and techniques so that you can better apply common sense.