My dining room decorating project

This year we hope to have our dining room decorated. Wallpaper off, carpet removed, radiators moved, wood panelling burned (whilst dancing like a heebeejeebee), sockets moved, new furniture, new alcove storage, a window seat with storage - you get the idea.  We're not doing anything structural in here, so it should be straight forward...

So we set to work stripping the wall paper off: wall & ceiling, to see what extent of plastering is required - just a skim? or completely replacing.Then we discover this quirky 'original feature' - the original plaster coving, discovered after removing some 'pretend' coving whilst stripping the wallpaper off the walls.

Once the crazy coving is off the walls we take the ceiling wallpaper off to reveal this baked-bean coloured ceiling.  Nice.

The we get to the fireplace, and take off some of the wooden panelling, hoping to reveal bare plaster....But no, we reveal...More wallpaper.

I should point out that this wallpaper is completely different to the wallpaper I've removed from wall and ceiling.  It's like they couldn't be arsed to remove this. This actually comes off quite easily, so I'm not so cross about this.But then you get to the ceiling, and see that it's a flush join with a proper corner.  Where has the plaster coving gone from this bit?  Oh, I see, they've chiselled it out so their nice wooden panelling looks neat.

So we've got this room, un wallpapered with 3 walls which have original ceiling coving (giving us no joins where wall-meets-ceiling) and on one wall with joins.

And a bay window which is about 6 inches lower than the rest of the ceiling....what do we do?

I know we'll lower the rest of the ceiling to match the bay window and not have to worry about the mish-mash of ceiling coving nonsense.