I agree with other posters that you should join the VA flying club - we are able to go premium economy both ways this year using a combination of miles and money, for the same cost as a return economy flight!!!! We always fly Virgin as they fly direct to Orlando from Manchester.
In the past we have used Expedia for our hotel and have always managed to get an expedia special rate so it's been cheap (disadvantage is you have to pay straightaway). For hotels we always start with Expedia, and then check people like Virgin Holidays and make good use of Google. This time we booked the Fairfield Inn through Virgin and we still don't understand how it was so cheap! (we have since cancelled as we are going with friends now and saying in a house). We have also booked directly with Disney when we stayed onsite - it is well worth buying an annual pass for the discount you get and of course the £ remains strong against the $.
Sorting everything out seperately does require a bit of leg work but it's always worth it IMHO! After going to DLP through a travel agent a couple of years ago (excellent deal) we always give them a chance to price match but they never can. Cars is usually the only area they can come close.
On the subject of cars, I always start by putting 'cheap florida car-hire' in Google - you get tons of results, but by looking at four or five you quickly get a feel for the 'right' price to pay and they always use one of the major suppliers (Alamo, Hertz etc). This also applies to hotels but I think you need an idea of where you want to stay.
For me, planning on the internet is the start of the holiday build up and although it can be frustrating, it's worth persevering (sp?) as you can get (IMO) a much better deal.
Four weeks tomorrow now for me and the plans are done, just need to get the $ and dust off the suitcases!!!!!!!!!