I was having lots of problems with poor speeds, which although not fully fixed is very much improved. During the Plusnet support back and forth conversations it was recommended to me by a PN engineer, to separate out 2.4 and 5ghz, as the standard config is an automated system, which according to the eng. gets itself in a pickle, and is a known issue. I followed his instructions and it did make a difference, now speeds and connection in the house were much better, faster and less liable to break. Word of warning, the process didn't apply WAP2 security to one of the frequencies, so you haver to go in to either 2.4 or 5 and re-establish it.
5 ghz was initially the faster of the two, reaching my limit wirelessly of around 33mbps close by, and 28-30 upstairs. 2.4 generally slower but still good and very useable.
Strangely tho this has reversed, but 2.4 is not as fast as 5 used to be.