Sure the scheme are promoted but try and reserve a plot/house of your choice and see what happens.
New builds around my area are plummeting, they are desperate to sell. A work colleague recently bought a house in July last year and paid £136k, which was a discount on the advertised price, and also got every floor fitted with carpet/laminate, kitchen fittings of her choice...
Now they are selling the exact same houses for £115k and I'm fairly sure they would accept lower too. They will also do the same as above in regards to the flooring and kitchen!
It's still most definitely a buyers market, and I'm sure a builder would take anything if you wanted to reserve a plot!