Sounds quite realistic to me.
We spent 10,000 on a three bed semi and most of the stuff we got was decent enough.
The allowance for the kitchen is quite low you will more than likely need to add a good bit to that but there are great bargains to be had on flooring if you look for them and similiarly on beds and bedroom furniture.
If you buy a lot of the stuff from the same place you can bargain, shop around and price everything in a few places, get quotes and use them to bargain if you like a particular item.