We have a house in Orlando, and travel out at least twice a year, and rent out at other times. If you can start looking early enough, you can usually find some good deals with Virgin and
www.lastminute.com
We have flown with Virgin, AA, Delta and Thomas Cook, Virgin was far and away the best airline to fly with, we are going out at Easter and have paid £290 each for the flights - with Virgin.
You get the added bonus of the Downtown Check in, which saves having to be at the airport early and wasting precious holiday time.
We always use Hertz for the car hire, it may be a little higher than some of the other companies, but if you register for the Gold membership, when you get to MCO, the bus takes you to Hertz, where a computer board tells you what row your car is in. You simply find the car (with the keys in the ignition and the boot already open), put your luggage in, and drive away! Much easier than having to go to the desk and have all the paperwork sorted out (especially after a 9 hour flight!). We found we can be out of the airport and driving away in 15 minutes! Sandford does not have the same option for Gold members, doesn't have as big a range of cars, and is further away from Orlando and the attractions.
Using our house as a price guide, I estimate you could have a family of 4 price around £1800-£2000 for flights, accommodation and car, all booked separately.
I have also found buying at least one annual pass to the parks can save you money in the long run. A 14 day ticket can cost around £170-£180. An annual pass costs around £230, but your parking is free, and you get discounts for shopping and dining. We find it usually pays for itself after 10 days, even if you only buy one AP, and normal tickets for the rest of your group.
Universal AP are even better value, around £115 for unlimited access, no black out dates, the same free parking, but more shopping and dining discounts. If you buy direct from Universal, you even get the option to pay monthly on your credit card!
I hope this helps, it may be easier to book a package, but not always cheaper!