Manoeuvring During A Charge
Unless stated otherwise, a charging unit cannot perform a
turn, move backwards, move sideways, redress the ranks or
reform manoeuvre during its charge move.
Drilled is the UNLESS STATED OTHERWISE part. This would support the word immediately.
As Drilled says IMMEDIATLY before a move. A charge is still considered a move 1.3 of the phase.
Drilled:
Some regiments spend endless hours training to perform
complex manoeuvres.
Unless it is fleeing, a Drilled unit may perform a free redress
the ranks manoeuvre immediately before moving. Once this
manoeuvre is complete, the unit moves as normal. In addition,
a Drilled unit can march whilst within 8" of an enemy unit
without first having to make a Leadership test.
To me, its clear that drilled units can charge from a marching column with an immediate/free redress of ranks.