With two days of SDSing, a couple of trips to the dump and a helluva
backache, this...

http://img833.imageshack.us/img833/759/oldav.jpg

....has become this:

http://img824.imageshack.us/img824/3737/newem.jpg

Next job is to repoint the brickwork, although it looks like some of
the perps are so thin that they never had mortar between them.

Regarding plastering, what is the best way to get an edge around the
opening? I was expecting to be able to fit a plaster stop bead but it
seems that the brick corners were originally broken off the vertical
sides, so this would leave something of a raggy edge inside:

http://img219.imageshack.us/img219/8198/edges.jpg

I guess I could try and remake the broken brick edges with something
like Tetrion (assuming the inside will ultimately be scrubbed and
white emulsioned) and then fit the plaster stop bead. Any other/better
options?

Also, what's the best finish for the arch edge? The steel lintel is
set back about 1/2" from the brick face:

http://img695.imageshack.us/img695/3689/steelw.jpg

Could a piece of stop bead be bent to follow the curve? Would it look
better flush with the bottom edge of the steel or with the brickwork
so the steel is still visible?

Any ideas why the bricks were originally broken in that way? I
assumed there was some kind of wooden staff bead (is that what it's
called?) there like on the external corners but I don't see why the
original builders would go to that trouble for something that was
going to be covered by a contemporary fireplace.

Thanks for any advice.