HI
Why not do the snag list your self, you know yourself what the house should should be like and you will be more fickle than a 3rd party. Important things to check is heating and electrcity. Arrange a time with the builder, take with you warm clothes, a torch (in case the electrcity is not on), a step ladder to get into attic, a friend (you will find that both of you will have different thins on your snag list) and patience. Take your time and don't be bullied by anyone on the site. remember this is your house once you move into it can be a nightmare to get things fixed after you have signed for the house.