Patchy Wall

[garry81]

I am in the process of doing up my bathroom and removed the old tiles from the wall.

This was fine although some of the plaster has come off and I now have large areas without any plaster at all. The remaining plaster was quite damp to start with but has now dried out.

I was wondering whether I would need to carry out any extra preparation before continuing to tile or should I remove all of the old plaster and tile directly onto the plasterboard?

Thanks in advance.