I've just completed the 2377-22. I would recommend it, if you want to do PAT testing in some capacity.
I wouldn't say it's a true level 3 course; the difficulty level straddles levels 1 and 2. I would assume the reason C&G have it at level 3 is because it's a 'professional' course and - again here I guess/assume - when it was originally set up it was probably intended as a supplemental award for electricians and trainees/apprentices rather than ordinary Joe Public.
I wouldn't say the course is 'easy'. For me it was, and from the perspective of an electrician it will be, but it's not going to be easy for an ordinary person. The course is over two days and is a pretty even split between theory and practical. You learn about the machine testing and Code-compliant inspection and testing. There are several practical exercises, including inspection and testing of 'live' equipment in use by the public, and there's a practical assessment in which you demonstrate competence in what you have learned. There's also a lot of classroom-type theory and a formal City & Guilds theory exam/assessment that is taken online under strict exam conditions and must be passed.
You need the two days because it's quite intensive - you need to know how to test different classes of equipment competently and confidently, you need to know the Code of Practice in great detail, and you need to grasp basic electrical theory and some of the mathematics, including Ohm's law (as a background), the power formula and the resistance formulae.
The exam requires an 80% pass mark - which means you can't blag it, you have to revise and prepare, no matter how clever you are. Yes, it's an open book exam, but you can't be sat there like Mister Bean thumbing through the Code of Practice trying to find explanations of stuff, as you only have limited time. Bringing the Code into the exam is essential, but it only helps in the sense that it allows you to quickly double-check things and also quickly look-up, or double-check, the testing exceedances and cable standards, etc.
I didn't find it difficult. I got 94% and was finished within an hour - but I have electrical knowledge. Others struggled. Sensible people do fail it.