Book everything online. Not sure where in the UK you are, but whenever I go , I use Flyglobespan. No frills, but hey it gets you there. If you check out this website
http://floridavillarental2.mysite.orange… and go to the last page, you will get links for discount carhire and disney tickets. Dont be conned into upgrading your car!! Just book the small one and you will get an upgrade Free of charge. They dont have the small 2 door cars they advertise. Well, I have never got one anyway and thats all I usually book. You are looking at around £100 per week for your car. Best getting a villa. You can eat cheap - shop at walmart and with the cost its much cheaper in the longrun.
Have a fab time !