I see you point and I'm sure you want to get your hands on it ASAP. If the car is registered 020114 it will be worth approx £1k more come trade in time than if it was registered on 31/12/13. Crazy I know but that's how it seems to work..
There isn't that big a value jump between Dec 13 (63) and Jan14 (63) - £300 maybe, no-one cares about the year as much as the plate. There will be a bigger jump at plate time Feb 14 (63) to Mar 14 (14) will see about a grand. For every other month between plates there is about £300 per month.
I saw this month to month change in my Scirocco in the Glass' and Parker guides in the 23 weeks I waited for my GTD from ordering. Aug 13 to Sep 13 saw the biggest dip,almost 40% of the whole 6 months depreciation between plates occurs in the month before a plate change, the rest is pretty incremental.