So, 750 kms and nine hours of riding later my thoughts are:
The K1200RS was a far better experience than doing this on the CBR250R (obviously). That said holy **** my legs and particularly my knees and ass are so ****ing sore. Good lord...
Speed - Well, legalities aside, I have found the speed at which I am most assuredly not comfortable. That being said, if I had full leathers, top notch gear and a brand new bike, I reckon I'd really enjoy a road without speed limits. The bike is a beast. Unbelievable power. Dangerously so. Also, a total and utter petrol whore. Would have been cheaper to take a bus.
All in all, it was an excellent ride. I enjoyed it even though I should have done it two legs, but overall, a great intro to bigger bikes and long distance touring trips. I am keen to upgrade to a more reliable bike and get full bore gear but one step at a time.
Exhausting day, but got me so wired, I've not been able to get a damned wink of sleep.