I've had a look at the AB book for grade 5 theory, and done a bit of playing around with the workbooks. It all seems very straightforward, and I'm worrying that I must be missing something. Is it fairly easy for an adult learner?

I don't think it is hard for an adult. Question 1 needs arithmetic and practice to spot the time signature. The melody question isn't too hard and the rest can be learned. To do the transposition I drew a piano keyboard and worked out the scales in both keys!
I learned it myself but a lot was what I had to know to play music.

B

Grade 5 theory is generally pretty straightforward. I won't say it's easy, but it is intensely logical, and so I'd imagine with the musical experience you have (and I don't just mean lessons, I mean all the music you do) you should be able to cope with it reasonably comfortably.

Cheers

Katyjay

Precious 8 year olds have to be able to pass it. Don't worry, you are not missing anything

Steve