Reddit mentions of TP-Link Wireless N150 Access Point, 2.4Ghz 150Mbps, 802.11b/g/n, AP/Client/Bridge/Repeater, 4dBi, Passive POE (TL-WA701ND)

http://www.amazon.co.uk/TP-Link-TL-WA701ND-150Mbps-Wireless-Access/dp/B002YETVVE
I use this to connect my ethernet-only Humax freesat box to my wifi (gives me iPlayer & ITVPlayer)

What you are looking for is a Wireless Access Point (WAP). A WAP is designed exactly for this purpose. They can range from £20 to £100 depending on quality and features. One of the cheaper ones would be fine for the purposes you described.

An example of one from Amazon.

If speed is not a major issue, you could get a NAS with build in WiFi.

You can connect most NAS boxes directly to a PC, but you will have to configure an IP address manually on both sides.

Another, slightly more complicated option would be to get a wireless bridge and connect the NAS and PCs with ethernet cables. This would get rid of any DHCP issues and allow you to still access the NAS without the cables as well when you don't need the speed. This does add extra cost and a lot of complications though.

Here is an example: http://www.amazon.co.uk/TP-Link-TL-WA701ND-Wireless-Access-Point/dp/B002YETVVE/ref=sr_1_6?ie=UTF8&qid=1380661153&sr=8-6&keywords=WiFi+Bridge

I use this one :
http://www.amazon.co.uk/TP-Link-TL-WA701ND-150Mbps-Wireless-Access/dp/B002YETVVE/ref=sr_1_1?ie=UTF8&qid=1344429090&sr=8-1

as an access point, also used it at college to broadcast wireless and now use it to get internet for my telly, great find.

Not a router, but a wireless access point. No idea why though.

Looks like your cable operator has installed a switch in your locality and is distributing using Ethernet cables.

1. Convert to only Wireless - Go for Wireless Access Point. (Sample)
   
2. Both Wireless and ethernet connection - go for router (Also Known as Cable Modems).(Sample)
   
   ^Note ^that ^routers ^are ^usually ^cheaper ^than ^access ^points.
   
   Coverage area:
   
   
3. Limited - 150Mbps (Single Antenna)
   
4. Medium to large area - 300Mbps (Dual Antenna)
   
5. Large Area - 300Mbps (Tripple Antenna)
   
   Go for detachable antenna - if you have wider areas.

TP-Link Wireless N300 2T2R Access Point - $24.95

[TP-Link N300 Wireless Wi-Fi Nano Travel Router] (https://www.amazon.com/TP-Link-Wireless-Travel-Extender-TL-WR802N/dp/B00TQEX8BO/ref=sr_1_5?s=pc&ie=UTF8&qid=1486583340&sr=1-5&keywords=Wireless+Bridge) - $27.99

TP-Link Wireless N150 Access Point - $19.99

I believe this is what /u/MeCJay12 is referring to. It replaces your existing ethernet jack in your master bedroom and turns it into an Access Point (while still giving you ethernet jacks to plug into).

• This setup assumes you either have a PoE switch or a can get a PoE injector for the new Access Point (I'm not too familiar with ubiquiti but someone might answer this).
  
  If you'd prefer to go cheaper than this, then you can pick up nearly any Access Point that can be powered by a PoE injector (example) and plug that straight into your master bedroom ethernet jack. If it can't be powered by a PoE injector then you'll need a power socket close to that ethernet jack (it will look a bit unprofessional).
  
  Edit: The Ubiquiti I've linked runs 802.11at PoE (an industry standard), which is blatantly obvious now that I've actually thought about it. Therefore you can easily get an injector if you'd want to go down that route (example).