Damaged walls. Should I re-plaster or use plasterboard ( Pictures included )

I would recommend to bond and plaster all walls around.

Is depends in that condition rest of walls, if good-repair with bonding, if rest of area bed condition-use plasterboard to make walls nice.

Personally I would say just board it. As the fixings would fix into the rear wall it shouldn't be an issue. Dot and Dab is very common. But everyone will have there own ideas and thoughts on this. Either way would be fine.

It depends what your budget is and what's acceptable to you. Making good the nessercary areas could be acceptable. The actual room without the units is part of the building fabric and in my opinion needs to be in good condition before you put the units in. If your budget allows and providing the remainder of the plasterwork is in sound condition then make good the missing plasterboard and get the room re-skimmed. Make sure you paint all the new plasterwork with a kitchen paint before fitting the units. This will seal the plaster and stop it absorbing any moisture created in the kitchen when it's in use. Then fit the units and splashbacks. if your tiling the whole room you don't need to skim just make sure what your sticking to is in sound condition. Kitchen units should never just be screwed to just plasterboard but the brick or block behind it which is easily done by using longer screws. In some cases for the wall units you may need to fill the cavity up so it's solid and doesn't compress when the bracket is fixed. It's hard to give total advice without seeing the issues but I guess that's the advantage of getting a tradesmen in to carry the work out. I would like to mention that an ill fitting botched kitchen will decrease the value of your home. If your not compertant get someone who is. We don't all charge a fortune for our experience and knowledge is well worthwhile. Best of luck on your project Hayden