Uponor underlfloor heating products - any experience? (and other things)

About to have an extension to a kitchen built (_when_ the party wall agreement finally arrives and is signed.. 6 weeks and counting now, grrr...) and we're using the disruption and opportunity to change the ageing combi and put in underfloor heating.
We're looking at a couple of manufacturers products - Hepworth and Uponor being amongst them, but wondered whether anyone had any experience of Uponor products, esp their underfloor heating solutions?
In particular, although a lot of information is available for their systems via the website, one question that isn't answered is which product to choose - PEX or MLC (multi-layer composite, I think) pipe and what the relative advantages of each are.
Floor construction is suspended timber - I'll install as much kingspan (or similar) as will fit between the joists and then fit the heat spreader plates on top laying the loops in the channels. 18mm ply on top (_VERY_ carefully screwed into position) and then ceramic/porcelain tiles on top. The new floor has to be concrete (apparently, to meet current building regs) but we'll level it to the height of the underside of the joists so that new joists can be run right across the width of the room & avoid having to undergo a screed/suspended transition on every single run of pipe. Area of room is about 25m^2, area of heated floor will be about 20m^2.
New combi will be Ideal Isar (or Icos, can never remember which is the combi...) HE30.
The other thing that I'm having difficulty getting to grips with is the area of heating controls and how the UFH control will interact with the programmable stat and the combi timer. I had thought that a fully programmable stat would negate the need for the combi timer, but heating engineer reckons not.
It would be so much more convenient to be able to control and program the heating from the hallway rather than having to open the boiler cupboard, and if a programmable stat capable of multi-zone operation can also control the UFH then so much the better.
Am I barking up the wrong tree with this?
And another thing... when running with a combi, is a pump needed in the UFH manifold, and how does this interact with the one in the combi - will there need to be a 3-way valve so that the floor can be operated independently of the heating of the rest of the house?
I thought I'd got it, but every time I think about it more questions pop up... (the Curse of the Software Developer ;-) )
Richard Sampson

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