Borders Man

I am building a single storey cottage. It will have an Air Source Heat Pump and underfloor heating throughout. We plan to put carpet in 3 bedrooms, but are receiving conflicting advice over the Tog value. Is it 2.5 Tog or 1.5 Tog for the underlay and carpet combined? Can anyone clarify? I think because we will have ASHP and U/Floor heating it is 1.5 but with the underlay at 0.7 tog it will be challenging to find a suitable carpet. All advice welcomed - thanks