I'm nearly ready now to come back again

Those of you who have visited our flat will know that we inherited a rather over-blown 1920's bathroom from the previous inhabitant. In the first instance I found it terrifying, but have grown to love its green and jet black tiling.

( I broke it )

But now we have the problem of fixing it. Anyone have any advice on filling large holes in walls? I'm worried that Polyfilla might just form a large plug that will pull straight back out again.