lining paper then paint?...

Will painting lining paper achieve a similar result to new plaster walls?

It's my sons room and i don't ave the time to be waiting for me to get hold of plaster, so i am thinking of lining it with 1200 lining paper and painting.

Will this achieve a finish similar to that of a plastered wall?

No

You can paint it and get a nice finish if hung properly.

It all depends on the quality of the walls.

Lining paper will hide some imperfections but not all. You may need to do some filling/sanding first.

I personally prefer to line newly plastered walls prior to painting even though I have sanded the plaster first. It makes the walls feel warmer and smoother to the touch (and the finish is more durable), but it is more expensive for the customer. Fortunately, most of my customers want the better finish rather than the cheaper one.