@Plajfnfir 

If possible, move the second adapter to another outlet that is located in the room it is as. I've seen big performance differences in simply move one adapter across the room.

Make sure neither is connected to a surge protector or power strip which can affect performance. 

If you are trying to load six cameras I would see what is the bandwidth it tries to push and compare that to what speeds you have available (speed test on a computer). So maybe looking at one camera vs trying to pull all six at once.

@Tony 

Thank you for replying. 
 

I spoke to someone at Currys in the end. The TP-Link helpline wasn't much use. 
 

Long story short, I bought a faster Tp-Link Powerline and it works a treat! 
 

To get the two to initially pair I plugged them in in the same room. I then took one to the loft and it worked first time. 
 

Plugging straight into the wall is also key, like you said, they don't like a power strip or power surge protector. 
 

Thanks again, if anyone on here has similar issues, the Powerline will work as long as it's plugged into the same house, the faster the model you can get the better 👍

Well... I'm not sure what you might have a problem with, but I've never encountered one. I have ajax wireless security cameras installed. You may have heard about this on the Internet or from friends. I don't know much about this topic, but I can always view the image from the security cameras on my phone through the mobile app without delay. Perhaps this is due to a good wi-fi connection. I think that you should read more information on the manufacturer's website. Maybe this will come in handy.