This has me mystified!

[David M]

Its a wooden floor and the mat is simply laid beneath it.

A floating laminate, or a tongue & groove solid wood? The solid wood tends to be glued and is generally more expensive and occasionally nailed, (which I doubt the floor fitter would be dumb enough to do this considering UFH is installed, or would he?).
Anyhow if the UFH installer is happy to come and sort it, that's just the job.
What will be very interesting is if you can find out exactly what the cause of the fault was and let us all know!! Cheers!

 

[HandySparks]

Just spoken to the installer (who travelled from Oldham to Surrey)...

That's pretty mad, especially when there's a risk of a callback. I shy away from jobs more than a few miles away.

 

[pe2dave]

Hi - I've not used that foil, it looks fragile for flooring installer use (sorry to be blunt). My 20p is one of "the 3" has been punctured and is in contact with the original concrete floor (?), but you'd think IR would be lower ... And the buzzing is the mat vibrating in the space between new flooring and original floor (not properly secured?).

Customer response to 'buzzing'? I know I'd just say fix it please.

 

[davesparks]

The foil type underfloor heating is a terrible idea in my opinion, I’ve seen it once before and I didn’t like it at all.

It is basically constructed like a rear window de-mister on a car, there’s a L and N bussbar formed by a copper strip running along each side of it with heating elements between them. All this is sandwiched between two thin flimsy bits of plastic.

 

[mattg4321]

Far better is something like the HeatMat Combymat, which I've used a few times under laminate/engineered wood flooring.

150W Combymat System - http://www.heatmat.co.uk/product-range/underlaminate-systems/combymat-heating-mats.html