OK, as everyone else has gone with Maz, my answers are in red...
Will the engine (and what an engine) do 100,000 miles? Who cares? If this is critical, get a Honda. If you want to have shitz'n'giggles rather than travel to the moon and back, get a Buell.
Will it rot in a British winter? Yup, if you don't give it some tlc, just like every other bike.
Real life mpg? 55 - but this is a motorbike purchase, not a new fridge.
Will it take a spill without bending that frame? Ah, no, not as standard, frame pucks and / or crash bars will work, though, just like they do on other bikes.
Will the belt drive last as long as a chain with a scotolier....do they break? Will one chain last as long as another chain? Strange question, each one is different but fitting a Free Spirits Tensioner will help. They should last 20k miles and they are easier and cheaper to change than a chain.
Two up and loaded will it get to Berlin.....and back Yeah, of course. Raiderfan travelled the length of America - that's the full deal, not just the US.
Can i get a helmet and laptop in those panniers? What panniers? The Uly doesn't come with panniers. If you mean the XT, then what helmet? The panniers will only carry Macs, not PCs.
At 6'2 will i have a face full of rain looking over that screen? The screens pop out, to change them takes a few seconds. I'd say it was irrelevant, if you need to change it, they cost peanuts (compared to the price of the bike) so don't sweat this one.
What will a full service cost...with a tyre and new pads for that disc?? Which service? Pads are peanuts too, about the same as any other pads, why worry about them? Tyre use on a twin is less than a 4 but you haven't asked about them.
Or...am i missing the point?.......
I'd say, by approximately the 100,000 miles in your first question. If those are your criteria, then get a Honda. It'll still break, it'll cost as much as a Buell and you'll be bored to hell.