My original question though was 'has anyone else been told about this' [earliest handover date of 17 March mandated by BMW GB] and as far as I can see, the answer seems to be 'no'.
That's not accurate. What you haven't heard is anyone in the UK receiving their new model 2014 1200 WC Adventure
ahead of the official launch date. You might be the only person to do so, depending on your powers of persuasion. Fingers crossed.
In July of last year you agreed with the dealer that your new bike would be delivered on the launch date, I can imagine the excitement. Of course nobody then knew what that date would be or whether it was cast in in stone that NO bikes would be released earlier. Of course you could have said that, as you travel a lot and work, you could only accept a Friday or Saturday pick-up and worked your calendar and theirs accordingly but you didn't. Whether that would have made any difference seems doubtful, as the launch date seems set for the Monday and no earlier. That means that you would have agreed that your earliest pick-up would have been the first convenient Friday or Saturday after the launch.
Your excuse that you buy flight tickets months in advance does not wash too well. Whenever it was you bought your tickets, you could not have known that BMW would mandate Monday 17 March, as you only learned that a day or so ago. It appears that by happy chance you just happen be near the dealership on Friday 15 or Saturday 16 and want your bike because it suits you; though you had agreed and established with the dealership that you would receive your bike on the launch date. It's just a pity that BMW have selected a very precise Monday, not the Friday or Saturday that you might have hoped for.
Had the launch date been Monday 24 March, what would you have done then? Would you have even been in the country? Would you have still insisted on Friday or Saturday the 22nd or 23rd? If so, it seems logical to wait the three or four days after the launch and pick the bike up then, perhaps? But if you are't going to be in the country as you travel so often and bought your tickets in say October 2013, you'd have been buggered anyway.
It all matters not as you are going into bat to secure an earlier release date. How successful you are (or whether BMW are persuaded on the grounds that you won't tell anyone) remains to be seen. What are you going to do if they insist on Monday 17 and you are not around the for following weekend or three, as you pre-buy tickets and are away a lot? Cancel your order? Sue them for damages and distress? Wait patiently? Torch the dealership and flame BMW through every social media outlet you can find?
Good luck in your innings but have your fallback position clearly worked out, the first or second delivery you face might be a Yorker on middle stump.