We did last minute 2 or 3 years back in summer hols. Was not easy getting something, depends how well tour operators have sold their hols.
We tried all major companies but they all wanted £800+ for a 2 week package. Ended up with a flydrive TCD which cost about £450 each booking day before we flew. I dont class that cheap for a last minute with no hotel maybe you do.
I usually check holiday.co.uk which searches major companies then if I find something go to that companies own website which is usually a little cheaper.
Done a quick check for a 2 week hol in Aug they are very expensive from London some decent prices elswhere.
Good luck