French path substrate - Substrate guidance

[LaCroix]

Hi
I am laying a small pathway at a small house I have in France. After speaking with the local stone specialists we went for 20mm thick limestone paviours to be laid in a ribbon strip pattern.They supplied a suitable exterior adhesive and grout together with a chemical sealant to be applied afterwards. When I asked them about how they would construct the tile bed they struggled to advise in English basically saying using cement and that my builder would know how to do it.
Having discussed it with the guy who is going to help me lay it we seem to be leaning towards a concrete substrate reinforced with either some steel mesh or fibre.
Does anyone have any thoughts on the best process. I am also installing some linear drainage channels in front of the house to carry waste water away for when we get torrential downpours and these will be concreted in. The current path is just gravel on top of the pretty hard French ground in front of the house. Path is only 4 metres long by about 1.5 metres wide.
Should we be going for layer of hardcore followed by reinforced concrete slab (if so what thicknesses etc) then adhesive and tile or something else?
Any advice greatly appreciated.
I have photos on my PC of the existing and proposed path but can't see how to insert them in this post!
Many thanks

The path has no vehicles using it

[lemoncurd1702]

100mm of well compacted sub-base will be ample and bed on semi dry sand cement mix of 50-100mm.