have a CCTV DVR that needs an ethernet connection to the router. Problem is they are at different ends of the house and will require significant effort to wire up.

Is there some gadget that could sort this via wifi? Could you plug some sort of wifi dongle in?

Would powerline extenders work for you?

This sort of thing

Power line as above is the way forward.

have to read into those more, but maybe, wifi range is fine, its more the fsct the DVR doesnt have wifi reciever and therefore needs to be hard wired.

You need a wifi-Ethernet bridge.

Homeplugs, as mentioned, will do the job. They freak me out a bit, using the electrical circuitry to pass the network signal down, but they work well. My Sky box is wired in this way – bought a 5 way power extender with a couple of ethernet ports in it. Homeplug at the other end connected to the router.

Would these do it?
https://www.amazon.co.uk/Powerline-Configuration-Required-TL-PA4010KIT-V1-20/dp/B01BECPIMC/ref=sr_1_1?ie=UTF8&qid=1492207209&sr=8-1&keywords=homeplug

Would they work if plugged into an extension cable, or do they need to be in the socket? Shouldn’t make a difference should it?

They recommend having them on the same ring and directly in the wall socket, but in my experience they work with one upstairs and 1 downstairs and the sender in an extension lead. Occasionally they seem to lose each other but a quick TOTO* and you’re good to go

*turn off turn on

Would they work if plugged into an extension cable, or do they need to be in the socket? Shouldn’t make a difference should it?

Yes they work, it just lowers the speed a bit.

You do get passthru models.

As above powerline £25 for a pair of wired Ethernet ones, also they do depend on house wiring / good connections but at £25 it won’t be too expensive to give it a go. I use TP-Link.

You could use:

https://www.amazon.co.uk/TP-Link-Support-Hotspot-Extender-TL-WR802N/dp/B00TQEX8BO in “client” mode

or

https://www.amazon.co.uk/Wireless-Dreambox-Network-Printer-Microsoft-x/dp/B005OIB6XI (I use one of these to connect an Ethernet-only YouView box to my Wifi network). Powered via a “spare” USB socket, you’d need a power adapter if USB not available.