Hi Clare,
We've been booking DIY for a while now. For our upcoming trip we booked Virgin through Virgin Travelstore, although we've used Expedia and Flightbookers in the past. We find phoning around is the best bet - the one that was cheapest last time won't necessarily be so this time. We also find that phoning seems to elicit better deals than booking online.
We usually book villas through one of the villa magazines available at WH Smith, although I like to get a good idea of what's about by surfing the net. I usually use Google and then keywords such as <b>Disney + villa, Orlando + villa, Kissimmee + villa</b>, etc.
In the past we've booked car hire directly with Dollar, but this time we've booked Dollar via Sunchase and obtained a substantial discount.