Laying B&Q 'French Flooring' planks

[Bomberman]

Hi all - seems like the place to ask this after some googling

Planning to lay the above on current floorboards. I've read around here and it appears that laying it floating and PVA glued is fine so I'm happy going that way. Couple of questions though (which may be daft).
It's currently carpeted and has some really nice foam underlay down - I'd hate to have to bin this as it provides great insulation (REALLY needed in the room) could I just leave that there or do I really need the fibreboard?
The DPM - is this necessary in this situation and why as the current floor doesn't have one? Tied to the above - should I put it above or below the underlay/fibreboard?

edit; Believe I've answered the DPM Q. - it's a no on floorboards

 

[WoodYouLike]

And it is a no no in regards of your carpet underlayment too I'm afraid.

Use an underlayment that is truly suitable for wooden flooring, carpet underlayment will crumble and is truly only suitable for carpets

 

[Bomberman]

Thanks mate. I was afraid of that, shame as it appears to be high quality (only high quality thing the previous owners appear to have used ).