Welcome.
Sounds like you have cash to burn, so fit a GKN overdrive to give you motorway performance, but not affecting your offroad / towing. Willl be better geared. I run a 110 TD5 on 50/50 muds and no, you won't be able to hear the radio at motorway sppeds, although an overdrive might help with this. I really like the Electronic Traction Control, and could help you extract yourself from the beach if you have issues, especially as the Shogun probably has a locking rear diff and the 110 won't. Air-con models are a bit cramped, but again I like the option. I've not seen the seat runners, but heard good reviews but maybe a little expensive for what they are. But then again, what''s your time worth trying to make them?! My advice really would be poach a loaner from a dealer for the weekend or hire one from SHB 4x4 just to see if you can put up with the lack of comfort, before you shell out a load of cash on one.
Extra's wise, just fit a EP9 superwinch with plasma on a standard plain winch bumper, and you with have understated non-chav bling, that will work when you need it too. That is all a road going defender should have, along with Wolf wheel rims.
So what boat do you have then?
Cheers,
Keef.