I've done the whole thread! Wow, that's some superb information! A few models certainly crop up again and again, so I'll be basing my research specifically on those. Like you Russ, I am more likely to go for something that can be bass heavy and I am certainly looking for something that reaches up in to that 'air' of top end without fatigue in the 2-4k region. - That said, I do have a dip in my hearing in that area, so it might even be a good idea to seek some extra advice if I am armed with my hearing test results.
I'm not too fussed about being hard-wired and I've had a few ideas about channeling my ear feed with my usual guitar cable without too much fuss. I will look at a suitable module to act as my level control / brickwall limiter etc when a headphone mix isn't available too. I think I'll concentrate on the in-ears first.
Really, thank you all for the advice - Russ, especially you.