(another variation on) soundproofing party wall
 

Hi
I want to add sound insulation to the party wall in our bedroom
(Victorian brick terrace), since the neighbours use theirs as a living
room - there's not a huge noise problem, I just want to make sure that
their conversation and TV doesn't keep us awake.

I've been reading old posts and I'm having trouble deciding between
whether to:
1) add mass to the wall with 50mm battens, 50mm insulation slabs and
plasterboard;
or
2)build a free-standing stud wall 10-25mm away from existing wall,
stuff with rockwool and cover with plasterboard.
(If #2 is best, should the rockwool go in the gap between wall &
stud-wall, leaving the studs "hollow" ? ; or should the rockwool sit
in the studs, leaving the gap empty between the walls ?)

There is another complication though - and do tell me if you think
that this will negate any noise reduction:
This is the only room in the house with an original cornice, and I am
loathe to cover/replace them, so I was think of only putting the
battens or stud wall from floor-level to just below the cornice. This
would leave the top 50/75mm of wall (with the cornice on) untouched.
I would have to cover and seal the gap at the top of the plasterboard.
(which, if I go for the stud-wall approach, would effectively join the
top of the stud-wall to the existing wall - hmmm
)
(I realise that it may look a bit strange too, but eventually there
will be some tall wardrobes along most of this wall.)

Given this complication with the cornice, should I go for solution #1
or #2 (or neither/other) ?
Cheers - Dan