Owning your own home

What do you and don't you need building regs certificates for? I'm struggling to find a definitive list.

I'm looking at three things and I'm not sure which, if any, require it:

1. Removing a wall in the kitchen to get a big kitchen rather than the original separate kitchen and utility room. I suspect not structural but not 100%.
   
2. Adding a downstairs toilet in what was originally the cupboard under the stairs.
   
3. Removing a wall separating the bathroom and toilet to make it all into one. Pretty sure this isn't structural.
   
   

Can anyone point me in the right direction.

Cheers