Window problems

[Explorer-8]

When I removed my old wallpaper around one of my windows, not only did the plaster come off, but there are gaping holes exposing the breezeblocks. I don't know what the area which surrounds the window is called except for the base area which is the windowsill. These surrounding areas have been made partly of wood and some have broken off.

My question is:
Will just plastering over the whole lot be enough, or will I need new sections fitting onto those corners of the window and the areas inside near to where the windowsill is? Does a window have to have what I think are called beads on the corners?

[MustafaTickl]

The area's of plaster returning from the main wall to the window are called reveals. Just clean off the defective plaster, make good any holes with patching plaster (from all DIY stores or builders merchants), apply a bonder over the lot, accurately set up a thin piece of timber (a lath) vertically to line up with the wall to finish the reveal plaster against, apply one or two coats of patching plaster to the reveals, remove the lath and make good the wall plaster up to the new reveal plaster.

[Explorer-8]

Thank you, MustafaTickl.

I know that I won't be using the builder that quoted me �1,500 to do the job - and he used a second hand envelope stuck down with a piece of sellotape.