Name the cable

[#1]

There is a good chance you have no issues at all. I think it may depend on the brand of adapters, and also how your wiring is routed, etc. I am sure there are a bunch of factors that can have an impact.
It is an easy check to make if you have access to line stats. You don't need to wait for DLM changes etc. Without line stats, I wouldn't have a had a clue about it.

[#2]

@ Mustrum
I would turn off the BT WiFi if I were you - as you aren't a BT customer you don't get the benefit of being able to use it yourself for free.

[#3]

As I said, I have ditched the Powerline Adaptors and found the Edimax N300 gave me better coverage Wi Fi with less noise and it is much cheaper than 2 Powerline plugs. My max download rate has improved a lot (shown in the ASUS DSL-N66U stats) and I am waiting for the DLM to adjust my line speed upwards (hopefully).

[#4]

@Jaggies
Alas I don't think there is a way of turning off BT WiFi, unless you can tell me otherwise?

[#5]

I have a BT HH5A and BT wifi is disabled. So it can be done. Only thing I did was a factory reset before configuring it. Then it was disabled by default.

[#6]

@jafreer Yes that did it, I have 2 HH5's must have forgotton to do this one. Cheers

[#7]

No benefit to have it on for the majority of Plusnet customers but I have a use for it since I am a FON member.
But then I have my Fonera broadcasting FON_FREE_INTERNET and use BT WiFi to check my FON login is still working 
NE