I have an existing narrow solid floor hallway, about 3.6 x 0.8 m. The
concrete floor has about 4-5 mm screed (concrete base is very rocky so depth
is variable), the house is old and sothere is no sub-floor insulation.

Do I have any realistic options for getting in underfloor heating - without
raising the floor level or digging up concrete (I might just be able to bear
digging up the screed - again)?. Would prefer wet UFL but would think about
electric - but not on uninsulated floor (to be tiled).

As far as I can see I'm snookered unless I can cram adequate insulation plus
a screed plus UFL plus ceramic tiles into about 40 mm.

The alternative would be very thin wall radiators - if such things exist!.

Paul