I've just looked at some prices and I recon I could do it for £4,100 - but that would be flying out one of the London airports (I'm Midlands so it always works out cheaper from Gatwick) but always direct flights.
Breakdown..
Flights-£2,100
Villa- £900 (off site but we've always had beautiful ones with lake views etc)
Car -£350 (midrange, add £100 if you want something nicer)
DW tickets £750 (add another £330 if you want Universal too)
Obviously you need to add food etc. on top but IMO that's very reasonable and we've found numerous great restaurants that eclipse all but the very best (and most expensive) Disney have to offer. We're not fnd of the 'free'
Disney dining plan as there are too many restrictions and it's supposed to be a holiday (plus the accom pricing is inflated on many occasions to make it 'free' IMO)
Also I think it's better to go as early in July as possible as the flights are usually a little cheaper.
Just my 2c