Puffin Killer,
Go for it...
During my CAA PPL training, I never received any serious training for using the various radio nav aids. It simply wasn't part of the syllabus. (I believe there's a little in the current JAR PPL?) My IMC rating changed my mental picture of navigating for ever. It'll do the same for you, I'm sure. VOR and NDB navigation is just as useful on a sunny day as on a rainy one.
Secondly, many IMC holders would agree that just the opportunity to fly VFR 'on top' is enough to justify doing the rating. It's a beautiful world up there, isn't it folks?
TW