Raising the inside temperature (heating) and adding insulation is, naturally, not practicable in what is just a shed after all.
So........... "crossflow ventilation" is what's needed. A simple way is to fit a 9"x9" (225mm x 225mm) airbrick high up on one wall (near the top of the masonry.)
Then, fit another, into the opposite wall. Fresh air will crossflow from one, and out the other one. This will help to equalise the interior and exterior temperatures.
This will greatly reduce condensation, and prevent fungal spores (mould/cellar fungus etc) from settling and growing on damp walls.