Sorry plaster guy!

[Ollyfp]

Good plasterers are hard to find, but I was lucky enough to find one, and he was FANTASTIC... and then I used a different one... and now I'm paying the price... (sniff).
Okay, I'll pull myself together. I've learned my lesson and now I need to move on.
So... I've finished breaking away the clumps of plaster at the bottom of the walls and I've filled all the voids where the plaster didn't quite reach down to the top of the 3" skirting (getting the picture yet?) BUT I'm left with one final issue...
The chimney breast was bricked-up and plasterboard was dot-and-dabbed over the entire breast ready for plastering. The plasterboard dipped in very slightly (5mm) where the fireplace opening used to be, so I asked the plasterer to add a little extra plaster to this area to make sure that the finish was flush, but... he didn't (no surprise there).
Anyway, I'm finally ready to ask what I came here to ask, and that is, 'How can I effectively bring the dipped area level with the surrounding area in order that the wall doesn't scream, 'THERE USED TO BE A FIREPLACE HERE!'?
Thanks people!

 

[Koolpc]

Cut it out and replace correctly...

 

[Ollyfp]

Cut it out and replace correctly...

Lol. Was hoping for an easier fix than that. The wall is solid as a rock. Just reading about 'easyfill'??
Thanks anyway!

 

[Wayners]

Seal wall. PVA 4-1. Use wood glue as PVA if you have some.. 4-1 will seal good enough with some suction still which you want.
Fill over dip and drag straight edge over to level.
Use a spirit level or bit of skirting. Anything you have. Don't be fussy just get it filled out. Damp sponge around the wet filled edges.
When set after an hour or more smooth over. Don't let first fill dry for hours. Get on it when set but still wet.
When dry sand with something flat like 120g sandpaper glued to block of wood. Use wood glue for that.
Mistcoat then paint.

Re easyfill. Can't say I like it as filler but will do job. Go with that

 

[Ollyfp]

Seal wall. PVA 4-1. Use wood glue as PVA if you have some.. 4-1 will seal good enough with some suction still which you want.
Fill over dip and drag straight edge over to level.
Use a spirit level or bit of skirting. Anything you have. Don't be fussy just get it filled out. Damp sponge around the wet filled edges.
When set after an hour or more smooth over. Don't let first fill dry for hours. Get on it when set but still wet.
When dry sand with something flat like 120g sandpaper glued to block of wood. Use wood glue for that.
Mistcoat then paint.

Re easyfill. Can't say I like it as filler but will do job. Go with that

Such a great answer! Just what I needed! Many thanks!!