Large height difference in concrete bathroom floor

I have removed the floor and internal cladding of a bathroom to allow replacement of all drain and water pipes. It's a timber frame on bricks with (removed) concrete floor.

I've discovered that the highest point of the bricks under the baseplate is about 80 mm higher than the lowest point. The red line in the picture shows height of highest point.



Previously, there was a cast iron bath in this corner with no floor beneath.

Thus when the concrete is poured, I think I have at least one of the following problems.
1. The concrete is poured up to the lowest point of the bricks, and there is a height difference that requires a very thick, sloping screed.
2. The concrete is poured up to the lowest point of the bricks, and the bricks protrude inside of the plasterboards
3. The concrete is poured higher the top of some bricks, in which case concrete is above the bottom of (and possibly above the top of) the baseplate.

Does anyone have any suggestions on how to deal with this?

How old is your house? Have you spoken to your builder? Is there anything on your plans and specs that reflects this?

Thanks for the reply. The house is 1940s. The bathroom appears to be an extension built about 1970.

I've since spoken to concreters whose suggestions have included.
- placing the lower part of the wall panels in place; and/or
- building up the base plate where necessary, and inserting expansion foam.