Laying concrete, how to keep it level?

[jonbuilder]

I am just about ready to start laying the concrete (100mm deep by 3.5m square) on my kitchen floor. I have already laid hardcore, sand, a DPM and polystyrene insulation.
I have taped the joints of the insulation board, and also laid a 6 inch high 'skirting board' of polystyrene around the perimeter, again taping it to the floor insulation.

1.)
Should I lay a second DPM above of the insulation board, and if so, should the 2nd DPM be lapped into the walls as well as the 1st DPM or can it just be trimmed at the edges of the concrete?

2.)
Despite my best efforts I was unable to get the floor 100% level after each layer (I am hoping that the concrete will be easier to level).
So before laying the concrete, are there any preperations I can do to make the job of levelling it out as easy as possible?
I plan to have the readymix pumped into my hallway and barrow it from there into the kitchen, laying it in 1/2 meter bands across the back of the room.

I have been thinking about ways of spanning the floor with some battening that is fixed to the walls, allowing me to drag a length of timber across the concrete at the correct hieght to level it, but this would mean puncturing the DPM at the edge.
Is this overkill - is tamping the concrete whilst laying it enough to get it level?
Does using a vibrating poker as well get better results?

I expect to have to use a self leveling screen once finished, but would like to get the concrete as level as possible first.

Thanks all for any responses,

 

[Symptoms]

jon - how to get it level? Tamp it level - batten to the walls above the finished floor level to create guides for the ends of the tamping board. Height differences - accommodate by taking out a notch at each end of the tamping board. It won't matter if you fix through your poly ABOVE the finished floor level. Kitchen floor, importance of it being level (later cabinet installation, etc.) consider buying a cheapo laser level or hire one to ensure the battens are right, don't rely on your spirit level. I was given a cheapo Black & Decker one as a birthday pressy by a neice (I wouldn't have bought it myself as I already had a DeWalt) but it has proved to be a terrific bit of kit; I think it cost her about £30. It's brilliant for tiling too.