Almost all ICF suppliers have a concrete flooring beam product that attaches to the wall. All normally show UFH embedded in these floors.

Am I being a bit dumb in suggesting that this is a huge thermal bridge / dump of 30'C floor heat into the 10-15'C concrete wall core. And hence a big waste of floor heating energy into the wall core.

Am I missing something?

I'm looking to design in wet UFH floors for basement, ground and first floor, but dont see how ICF decks can be used on the ground and first floors without thermal bridging to the walls, ( basement will be insulated slab )

Someone please tell me I am being stupid !!!

You are not being dumb, you have found the problem with the use of eps floor system. The only way to lessen the impact is to beef up the exterior wall insulation. I see by your rendering that you may be using Quad Lock. They allow you to increase the thickness of the exterior insulation. This is one reason I don't use this product in my area. Chasing the toasty floor has it's cost.

...

cliftonarms I agree with you.....do a wood truss floor with an inch and a half of concrete on top if you want heated floors.