If you really want a limo, I think they are outrageously priced for the 45 minute trip to WDW, you could go into the internet and search for a limo company. If you go to any transportation company they usually don't have limos and end up subbing out your ride to a limo company, usually charging you extra so they can make some money. Remember when you speak limo you are talking about a big stretched lincolm or hummer. If you want a sedan, SUV or van that is a different story and you will find prices down to earth.
If you are looking for just regular transportation form the Sanford airport you might go to their web stie and call a few of the companies listed there. It is best to use the companies permitted at that airport because they have submitted proof they are responsible for you by following the requirements for getting permitted there.
Don't wait, set up your reservation ahead of time because if you get there and have to use the taxi system you will end up paying $130.00 one way to WDW. The car service from that airport will run you somewhere between $180.00 - $220.00 round trip depending on the company you choose..