Hi Iain,
The advice above is all spot on. The City & Guilds / IET course books are pretty essential (just get the level 2 book for now), they are as you say very targeted to the learning outcomes (what you'll be assessed on). If your college is signed up to the C&G SmartScreen thingie, that's well worth a look as well. To complement the course, the Trevor Linsley books (Basic Electrical Installation = level 2, Advanced Electrical Installation = level 3) put a slightly more colloquial slant on things. They follow the syllabus pretty well, and are very readable. The Chris Kitcher book ("Practical Guide to Inspection, Testing, and Certification of Electrical Installations") might be useful later on (probably not so much on level 2) as it has lots of photographs and explains that aspect of the trade very nicely (be aware, though, there are quite a few errors in the example questions and some of the theory is a bit out of date, in the 3rd edition that I've got.)
There are quite a lot of formulae, yep, but the important ones you will use so often that they will sink in, and the less important ones you'll just have to cram for the exams, and thereafter know where to look to find them and how to apply them.
The level 2 course has a lot more practical emphasis, and is probably the most "fun" of the two. By the sound of it you'll breeze the practical stuff. The level 3 stuff is mostly theory, but there's some great stuff in there about fault finding, inspection and testing, and installation design.
I start teaching the Level 2 course on Tuesday for the first time (so I guess I'm a trainee tutor, lol!), or the theory parts of it at least. Meanwhile I am just starting my NVQ3, so still very much learning on the practical side of things. If you've got questions on theory or concepts, then give us a shout... we won't do your homework for you, but we'll be very happy to help you get stuff sorted in your head.
Very best of luck on they journey, and enjoy the ride!