New building regs

Hello I'm hoping someone can answer my questions please ; I've recently bought a rustic plot with a 1 bed log cabin and a small build 1 bed + bathroom casseta  I'm moving over permanently next year and would either like to extend the cabin or remove it ..replace it with something bigger and extend the other building am i allowed ?

That has to be discussed with the local town hall and maybe include your architect.

Town council were the land belongs to?

As we seem to be splitting hairs when using various forms of English

Try the ayuntamiento municipal for the area where the property is located