Thanks, Roberto. Is there a particular reason to choose Plusnet? It does seem like they have good value products, but I wonder if providers like A&A, ADSL24, Xilo or Vivaciti are worth considering--though they look to be 15 to 20 pounds a month more expense. They seem to promise an especially robust connection (lower latency, less congestion etc.). Is that just marketing? And ADSL24 offers the C&W LLU--is that any better?
I think you've largely hit the nail on the head yourself there

.
All the ISPs you mention there are in the top rank for quality. All get the occasional complaint, like any ISP, except A & A (AAISP) who very rarely do. I must admit I haven't looked into AAISP's recent
Home::1 product, which looks to be a medium-usage cheaper offering. Their long-standing ones are very pricey unless you only use them outside daytime, and that explains why they are able to offer such a good service.
The others use combinations of BT Wholesale, O2 Wholesale, C & W and TalkTalk Wholesale, with overlapping and far from identical packages.
I'm not sure where you get the "more robust connection" from, nor the lower latency and less congestion. Two years ago I think you would have been correct, but with wholesale prices falling virtually all the well-known ISPs have upped their game hugely in that period. If you see any claims anywhere about 20:1 or 50:1 contention ratios, those went out with the ark. They refer to BT Wholesale products that are no longer sold.
I would say all of the ones that have been mentioned are viable choices.
BT Retail, Sky and TalkTalk get occasional geographic pockets of congestion, like your VM service. But it seems not as badly or as numerous/widespread as VM. Sky appear to be the quickest at upgrading where necessary once it occurs.
Plusnet have systems monitoring their loadings 24/7, for example see
this page, and you will find
this post by the
Head of Products and Digital Care, when replying to a doubter about
this description of Plusnet's traffic management system.
Throttling details.
Traffic management system.
Support differences between ISPs are a major factor. BT Retail in general have a poor reputation, Sky quite good. TalkTalk quite poor on the support lines but good support from their staff on their in-house forums.
Plusnet are currently having a bit of a bad spell with first-line support being slow to respond compared to in the past. The Plusnet internal systems have also grown in a somewhat haphazard way over the years and are rather cumbersome - which doesn't help first-line support

.
On the Community forums members of the
Digital Care team, (see Kelly's job title above), are present every weekday and often at weekends. They also visit these forums frequently but obviously not as much as there.
They are bright cookies and do have the power to kick things into action within Plusnet. (This sounds a bit like what reputedly happens at TalkTalk). If there is a problem with Openreach however they can get stuck. AAISP is the best at dealing with Openreach.
I would rate the support from AAISP; ADSL24; Xilo/uno and vivaciti as good. Of that type of ISP it's also worth looking at Aquiss. I would not go anywhere near UKFSN.
Thus spake the Plusnet Marketing machine

. I still feel Plusnet are currently the place to be, and I have highlighted their strengths and weaknesses. There's quite a lot above for you to chew on. I'll leave you to form your opinion of my probity and judgement

.
My broadband basic info/help site - www.robertos.me.uk |
Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 54.2/15.2Mbps @ 600m. -
BQM
"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
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Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.