Bath thingy

[ryetee]

I want to replace the bath thingy. Not sure what it's official name is but I'm talking about the chrome strainer where the plug itself sits. Mine has a screw in the middle. It's it just a case of unscrewing that and replacing with a suitable sized new one. Or will the unscrewing cause the bit underneath the bath to fall away?
If the latter I presume I'll have to take the bath panels off which will be a pain.

 

[Burnerman]

We can call it a rose, and if you take the screw out the piece underneath- the trap - may disconnect.
The rose and the trap are coupled together with that screw.
John