More DIY Queries - This Time Plaster...

[Monster]

I've got 2 (hopefully) simple questions regarding some works to a house I am trying to tidy up currently.

1. In the bathroom I have taken off a huge amount of wall tiles which have also taken with them a good chunk of the plaster. They are on the external wall, party wall and internal walls. I can't afford to lose any space or the bath will not fit down the far end (1700mm). Is there any good patch repair I could use to make the surface good to paint or is it a better idea to knock it all back to the brickwork/blockwork and replaster fully?

2. In the kitchen below the bathroom I have a similiar question. However with the kitchen I've been advised to batten the wall out and board it to allow the new ring main to run more easily. Is this a sensible idea or should I be trying to plaster over the wires again?

See pics below of both. Thanks in advance.

 

[Monster]

I used this in a kitchen and though it was rubbish. After a year or so it crazed and needed to be redone.

What does crazed mean? Fell off? Did you have tiles covering yours also?

As I understand it, wires need to be in metal trunking if just under plaster.
Hire a wall chaser, make the mess now.
I'd only board out if I was adding insulation underneath because it was a cold external wall.

If the bathroom plaster is sound then patch, if it's like sand held together with snot, then redo.

I was a little worried about chasing the wall as the brickwork looks a little rough under the plaster. I guess I just cut a small chase and then use a hammer and small chisel to get the depth?

The bathroom plaster is fairly solid but a little sandy, so I'm a little worried about it actually holding stuff.

I guess a replaster is the best solution if money no object (which it is though!)

Cheers.