Hiya, so long as there's rooms available in your chosen hotel there should be no problem with changing. The charges will depend on the date your due to go as fees vary, the sooner your going the higher the costs may be. Your probably looking at a minimum of £50 plus any difference in cost. If the new hotel is less expensive and you've already paid the full balance, I would look to add extras with that extra money rather than lose it. If you've only paid a deposit and there's no travel included, you may have to surrender your deposit and rebook, but without knowing more about your situation, it's hard to say.
Is it deffinately disneyholidays.co.uk that you have booked with? If so, they are an agent and not the direct Disney company. Disneylandparis.co.uk is the direct site, and are a bit more flexible.
Let us know how you got on, I hope you got it sorted
