I did think of that (thanks for the tip anyway!), but decided I couldn't be arsed. The spooks are going to ignore the guidelines anyway, I expect, and after the surreal "it's now legal because you know about it" moment thought it was probably just going to be bollocks anyway.
Personally, I've decided to take a leaf out of GCHQ's book: Totally ignore any rules and encrypt whatever bits of my data I damn well feel like at the time.