I don't see single extender either, then I decided to purchase another KIT, so now one is connected to my router, the other three are plugged into other rooms, and they all work fine(except of one in other room has no wifi, only provide wired connection)

If that's a house not just an apartment, go with AV1200 standard for much improved throughput on multiple clients. Also, for the sake of working Iive IPTV, all your network equipment must support "multicast" streaming, aka IGMP.

Since TP-Link's firmware has been patchy both in terms of throughput and reliability as well as IGMP being supported, I strongly recommend you look elsewhere. German manufacturer devolo have been amazingly consistent in getting both hardware and firmware perfectly right - and they do make UK models of their gear. If you have access to your house wiring, and the router is near the main fusebox, you should most definitely have a certified electrician mount a "dLAN pro 1200 DINrail" right in there and have the internet router feed directly into it. That little thing comes at a cost, but it makes a world of difference in terms of speed and reliability. Then cater to your endpoints with whichever 1200 series device fits best.

Devolo's WiFi-enabled 1200 series adapters come in a kit with one simple PLC adapter, or in a kit of three, or as a single unit - as you please. They also have a system that lets you easily share the same WiFi credentials across all adapters.

[SUB]Many thanks for the replies. Having now received confirmation from Tp-Link that Gbit wifi adapters are not available for sale as single units in the UK at the present time, I have decided to follow Peter Ms advice and go with the Devolo AV1200 units. May also follow up on the other advice re: dLAN pro 1200 DINRail when I have looked into it further. Your replies appreciated.[/SUB]