Hmm, after reading through this thread, I went and bought some ER-20s. No hassle, they're only like a tenner or something. Took them to our last band practice, set everything up how we wanted it, and then in went the plugs. Immediately, I felt like something had been taken away from the sound of the band though. The tones and effects we use weren't coming through well at all, the drums were barely audible sometimes, and everything just felt dampened. To be honest, this kind of killed off a lot of the enjoyment for me, as I couldn't cope with this alteration of what I hear. After 15 minutes, I abandoned the earplugs, and exposed myself to sonic bliss again, much to my relief.
So I'm left with somewhat of a dilemma. I know that earplugs are going to save me hassle in the long run - my ears are obviously incredibly important. But I just can't work with them. I can't imagine doing a full practice, let alone two a week with them in, and gigs would be a nightmare :/
I'd love to have something that just quietened the sound, rather than put a blanket over it, but I don't want to splash £150 on a fitted pair, if I can't be sure I won't have the same issue.