What even is a POE switch?
It's a switch that supplies Power Over Ethernet. It's a way of powering devices over network cable. It not really necessary if you just want an Access Point. It makes more sense if you realise what people call a "router" is actually a box that contains the functionality of a switch, firewall, router and wi-fi all in one. A router needs to do all those things, but if you only need an Access Point, then you don't need the rest of the stuff, just the wi-fi and bridge functionality.
So I'm slightly confused as to why people keep mentioning the router option if its not gonna work well? I dont mind buying an access point if it will work well.
People are talking about routers, because you said you had a spare one. A good router could be dropped into AP mode and work, but an Access Point would be the right tool for the job if you were going out to buy something to do this job.
The router option would work if you had a decent router you could put into AP mode, but the BT Homehub 2 doesn't have that because it's a very cut down device. You would have to do some configuration bodging and it wouldn't be happy or work as well as a AP.
Do I just plug the ethernet into the access point then thats it I have wifi in the room or is there more configuration associated with setting it up?
You plug it in, connect the ethernet, then there's probably some minimal configuring, rather like the wi-fi section of your router. You would just connect to the AP from your network just like you connect to your router, but on a different local IP address. Then you set up a few things (there's probably some kind of wizard to guide you through).
Also, why a couple of AP? Do I need more than one for my room?
Only if you need extra coverage. People might have mentioned more than one if they were talking about mesh networks, which are something else you don't need to worry about.