There isn't really any such thing as a good range extender. They are flawed by design. Best option is run a cable from the router to the area you need coverage, and get a basic access point to cover that area. 

If that isn't an option, you could consider a powerline kit - these don't always work, and aren't 100% stable, but in most cases are better than a range extender. 

If you are really set on a range extender, something like this should do the job. 

What are sky offering you and for what price?

Sky extender is $10 a month on hire - not sure if they sell the item but would be out of my price range.

The extender that you mention would you know if it would work with Sky router nz?

Thanks for you interest.

Sure, $10 per month adds up. Any range extender will work - they are basically generic. You do want to make sure the one you get supports at least 2x2 Wireless AC for the best possible performance. That one I linked to does support this. 

https://www.pbtech.co.nz/product/NRETPL5300/TP-Link-OneMesh-RE300-Wi-Fi-Range-Extender-Dual-Ba

That is a cheaper option that should still perform acceptably. 

Okay, thanks for you help. My concern with the Sky router was in case it's customized because they offer an extender of there own.

Thanks again.

Iceni:

 

Okay, thanks for you help. My concern with the Sky router was in case it's customized because they offer an extender of there own.

 

Thanks again.

 

They offer an extender of their own so they can clip the ticket at $10 a month that will likely pay for the cost of the device within 18 months, and then its all gravy for them... :)

Hi, might I suggest that any extender you use, dont connect it to the main router via wifi, run a cable instead, the primary fail of extenders uplinked via wifi is they either store and forwrd repeat which immediately halves through put, or they use one of the bands to uplink leaving you with just the 2.4GHz band on the extention unit, both solutions are dumb dumb dumb.

Run a cable, use any decent AP as the extender.

Cyril 

Just to query the base assumptions, can you give us a basic idea of the physical layout of your place? 

How big is your house?  Multi level?

Where is the router currently located?

Which areas are getting less than ideal performance, and what sort of access do they need? 

Can you run a network cable to a different part of the house?  Under floor?  In Ceiling ? 

From my personal experience with Sky Broadband, the WIFI coverage is sufficient to cover our house - but it is relatively compact single level.

It is an improvement on the HG659 router I used before - the WIFI now covers the far end of the house reliably with a strong signal, whereas previously it was just 'so-so'. I didn't need the booster.
But as mentioned by other people rather than using a wifi repeating station, running a network cable to a new access point is preferable.

Ensure your extender of choice has an ethernet port and supports "access point mode". You then hard wire it back to the primary router.   

The best suits-everyone product for consumers extending wifi in a single building is a TP-Link Powerline Wifi extender kit. Such as the TL-WPA4220Kit