haven't seen thuse here, stuart,,, is that a true screed OR a filler panel ? guess it depends on how 1 defines 'screed',,, i'll look for them at world of concrete - don't recall seeing them the last time but
my thoughts on this - either extended polymer-modified cement, bonded, OR unbonded overlay,,, pm cement's going to be expensive; bonded requires more prep than just dia grinding & will probably exhibit random cracking when done; or the unbonded
1 could also hire in a gypcrete crew
the easiest for a diy'er is, imn-s-hfo, plywood on top of wood