Which word do you use?
Growing up, we used to say settee, but at some point, we switched to sofa. I'm a Londoner, but my mum was from the Midlands, so I think that was a regional thing we got from her.
Sofa. I'll accept settee but couch sounds weird. I don't think I've ever heard anyone use it outside of American's taking the piss out of Vance.