Wow, thats a lot of information to digest in such a short amount of time lol. So much so that I won't try and reply to every individual comment. I'll just summarise...
Firstly, I will be fit for purpose. I plan to do a combination of (and not limited to one) 100, 200, 300, 600km rides...I also plan to continue running (GSR and a half marathon in a few weeks time!), going to the gym and doing anything else remotely active that I can fit in. I understand the concept that endurance comes from me, not the bike etc.
As for what I plan to do after LEL (apart from walking like a penguin for a week)... I will probably go out for weekend blats with friends, of anything upto 100km at a time really, i only live 2 miles from my office so not worth the commute.
Is there some magic all rounder? I guess what I'm saying is I dont want an out and out twitchy race bike...but it dont want some sloppy lethargic road bike either. Would the bikes mentioned way back in my first post meet this 'middle ground' requirement? I'm thinking 25mm tyres will be my first choice based on what has been said so far.
Oh, and if mudguards are going to help then i dont mind some clip on jobbies. I'll probably settle for a saddle bag rather than full panniers.