Hi Stephanie,
How exciting you're planning your holiday to Disney :-)
Both November and January are very good times to visit WDW as the parks are at their quietest, but there are a few dates you should try and avoid. I'm not sure which year you're thinking of visiting but the ones to miss are Thanksgiving, which this year is on November 26th and Martin Luther King Day which is on January 18th 2010. Google will be able to help you find out other years if required.
Personally if I had the choice I would choose to visit mid November, leaving before Thanksgiving, as most of the Christmas decorations will be up and they're truly beautiful plus the weather is still very warm, well to us Brits it is!!!
As such a huge part of the cost of a Disney holiday from the UK is the flights it may be worth just pricing both dates up and seeing if there's a big difference. Also buying your flights direct and booking the Disney part of your trip direct with
www.disneyworld.co.uk can save you lots of money.
Hope that helps and I'm sure whenever you choose to visit you'll have a fantastic time,
Jo