Uneven kitchen floor

[Starfish50]

I've knocked through my kitchen to my dining room and am now looking at what flooring to put down. The timber on the dining room side is bowed, I have a line of brickwork where the wall was and the kitchen side is lino.
I was thinking of LVT but have been told I can't do this because of the uneven floor. What is the best solution to this? Do I have to get the brick ground down to the level with the floor, then try to use self levelling stuff to make the rest of the floor level. Or could I use ply board? Also I can't do this myself so do I need a builder or joiner?
Any advice gratefully received.
Thanks

is it a wooden floor? Laid on wooden joists with a space underneath? Which is ventilated by airbricks in the outside walls, below floor level?

Or is it a concrete floor?

How old is the floor?

The kitchen side looks to be concrete and the dining room side is a wooden floor with joists and space underneath.
It's the age of the house so 1930s