Underfloor heating - is there an alternative to screeding

The foil wrapped under floor heating is generally for under laminate/wood flooring. The heating mat is laid on top of a foam underlay and the finished floor directly on top of the foil heating mat. For under tiles you need to use an underfloor heating mat that has screed over the top. So all depends on what your finished floor is going to be.

Yes u would need to cover the matting in a flexible latex or a form of fracture matt

Electrical underfloor heating matting is a very versatile product. With the foil wrap it can be laid directly under wood or laminate flooring for providing the source of reflective heat and can be laid under tiled Floors too without foil. When installing on a wooden floor a suitable flexible matting such as ditra should be installed first with adhesive electrical wires laid. And then tiling on top of that. This protects against movement cracking as the wooden floor moves the different rate for the tiling

Under tiles, a suitable electric underfloor heat mat or heat cables need only be covered by the tile adhesive. Foil underfloor heating systems are typically used under laminate flooring.