Can anyone tell me the name of the ubiquitous lumpy paint used on the interior walls in Spain? I want to paint one of my bathrooms in the UK with it.

I think you will find its not the paint but the product applied to the wall first.

Lovely, thanks. Do you know what it is that has been applied. I tried to explain what it was like to my painter last year but he applied sand textured paint and it's dreadful.

I think what you are referring to is simply render (cement, sand and water) that has then been sponged rather than floated - gives a much rougher finish.

Thanks, not as simple a task as I had thought. Plan B is to take a sanding disc to the walls.

What one normally does in these circumstances is to have them skimmed with plaster (yeso) - by no means a small task.

Sanding of render isn't possible. However, give it a go and let us know as my theory might not be correct (about it actually being render).

It´s called Rugoso. It´s not a paint, you paint over it. You can find it on Google. I´ve used it inside and out and, while you´ll never be able to match the finish perfectly, it does a good job. It may be what your builder used. You can get it in fine and course, interior and exterior. You can apply it in various ways but I have a sponge roller with holes in it that I bought from Leroy Merlin.

It is like plaster that is quite runny & its applied with a spray gun that "spits" it out onto the wall, this can be via an air gun & I have seen a mechanical type used as well.
When dry you paint over it & its very durable with the bonus of hiding an imperfection here & there.