tile adhesive

[Wool]

I have finally managed to remove all the ceramic tiles from my 70s style bathroom ( well,paid my 15yr old �50!) prior to fitting a new bathroom suite & shower. All wall were tiled and I know they will need replastering before new tiles/painting (by an expert, not me!)]
Problem - 70% of them left their adhesive behind, v thick and v difficult to remove. Have tried sponging down with water & a wallpaper scraper, but still lots left.
Does it all have to be removed, and how can I do it?

[Alibobs]

We had our walls replastered over the adhesive. Ten years later still going strong

[woodchopper]

Try using a belt sander - but beware of the dust.

[Wool]

I like the idea of just plastering over, thanks! (got a weekend back!)