Insulate under floorboards or thick underlay?

[mondeoman]

As the title says really..

Lounge carpet is coming up shortly and its a suspended wooden floor, with about 2' clearance underneath, fully vented with air-bricks, and its always been a bit draughty and cool under-foot, even though it is carpeted. Do I go to the hassle of fitting insulation under the floorboards, or will a decent modern underlay (12mm Cloud9 or similar) do the job just as well (and a lot easier). I can do 12mm as there are no doors to trim.

[mondeoman]

Celotex sounds interesting, how did you fix it in place?

[mondeoman]

oooh there's an idea - can I rip up the old T&G, put the insulation in, then replace with flooring sheets??