Using a second router as a Wi-Fi extender.

[#1]

I have recently purchased a Wi-Fi extender, but it seems to have a really poor signal extender and I'm unable to connect my devices in an outbuilding to it, even though it is located between my Plusnet router and the outbuilding. Some devices in the outbuilding actually can't find the extender, but will find my Plusnet router which is located in the house! It would be a lot of messing around trying to hide an extended DSL cable if I was to move my Plusnet router nearer to the outbuilding, so I was wondering if I could purchase a second hand Plusnet router and connect it wirelessly to my current router, placing it nearer the outbuilding? I've read posts where people have connected two routers using Ethernet cables, but again, trying to hide the cable would mean removing skirting boards and floor edging. I've also looked into the possibility of using Powerline Extenders, but the outbuilding's sockets are on a different circuit from the house's socket circuit.

Thanks in advance for any help.

[#2]

@Neil_M 

In a word, No. You can use a second hub as an Access Point using an Ethernet cable. 
You could always try Powerline, it might work, be it at a reduced speed. 
Your best bet is to mess about as you put it and install an CAT5e NOT DSL Ethernet cable between the two locations and fit an Access Point at the remote location.

[#3]

Thanks for the quick reply @Baldrick1.

At the moment I'm using a Mi-Fi box located in the outbuilding with a 4G sim card in it. Apart from paying for a monthly data allowance, it works really well. The only other downside is that I can only connect 10 devices to it, which isn't good when you have 14 devices requiring a connection!

I don't think there's a limit to how many devices I can connect to my Plusnet router, so I may as well just move it closer to the outbuilding and have everything connect to it from there. 

[#4]

@Neil_M  Have a look at this....

https://www.ebay.co.uk/itm/285185066956?

can connect up to 64 units ! . works on all SIM only ... ( check out SMARTY for  using theTHREE network - no annual increase, monthly contract... can inrease or decrease the level of DATA each month as necessary. )

Note this guy is a "good supplier"... have used him before, and very helpful with tech queries.

he has various "grades" so be aware of that when looking at prices.