If you are doing near 10-12k miles, I wouldn't bother with having to service it asap. Servicing is subjective and a book or a computer shouldn't be the be all and end all for when you should service. 12 month service is a good idea to do anyway but it doesn't need to be exact, even if it is 6 months later and the engine oil level isn't low and the oil isn't too burn't and the milage is fairly low, there is enough coolant in the radiator, you shouldn't have a problem. Milage is always a better indicator for servicing intevals over time, unless you don't intend on servicing the car for 2 years or longer...
Also my GT tells me when a service is due which just gives a rough idea of when it should be done, but it definately doesn't take precedent over when I think the service is due.
Also you can never service a car too much, by service I mean simply changing fluids, most of the other stuff done by the dealers is a waste of money or not necessary every single service. A car with tip top fluids is going to be much better in the long run than the average person who takes their car for a service because a book or computer tells them to. Before a service is due (especially in diesel cars) it is common for oil levels and coolant fluids to fall below the minimum mark (depending how you drive it). Chances are you will have to top up the oil or coolant before the book says to service it anyway.
Being on time for a service is always better for resale though.
So basically if you think something will go wrong if you don't service it right on the 12 month mark, don't worry too much, as long as the fluids are within the acceptable levels the car should be fine for a few months.