Ave cost of skimming walls

We've just moved into a 1970s house and as you'd expect there's artex everywhere! What's the average cost of covering artex with new plaster?
We need the hallways upstairs and downstairs done, and the stairs themselves. We also removed wallpaper in the living room only to find horrible walls underneath so that needs doing too, as I don't think lining paper will cut it, at least not with our limited skills.
The living room is big 19.5'x15.7', I don't know the measurements of the hallways etc.
I'm just looking for a rough idea so I can get some quotes and not be too shocked! Cheers.

It's a hard call without seeing the job.

Artex isn't the nicest product to work with, and I have no idea of the Artex style you have.

The bottom line is the deep the Artex feature the more work it will need to get to a smooth new skim finish. The normal format is masks and industrial sized scrapers to remove the high points, pva coat x 2 and then skim.

Sometimes it's quicker and more efficient to board over..

My plasterer charges £150 a day cash and will bash out a prep ready mid to large room in 2 days. Add on £40 for plaster.

As a very general guess I'd suggest a solid weeks work man and boy £1000 plus materials.

Interesting to get a London price - Kent may be a bit cheaper, as it is here in Sussex.