So, BT are advertising on TV that they have the "most reliable broadband*"
(* Compared to other up to 16 Mb/s providers)
This seems an odd claim for several reasons.
For a start, all of the other BT Wholesale based ISPs have the same underlying backhaul, so will be the same basic reliability. That means hundreds of other providers are just as reliable, making their claim a bit odd. I would not use "most" to refer to "equal first place with 100 others".
There can be a difference in provider though, some will be way more tenacious about fixing line faults, and oddly, A&A are known for that, even within BT.
But most importantly, as far as I know, BT do not do anything like A&A Office::1 package. This is two or three broadband lines, usually with different backhaul providers, and 3G backup configured to provide high reliability. It is provably more reliable than one broadband line. If BT don't offer that, but A&A do, then, well, who offers the most reliable broadband?
So, it seems, in my opinion, that BT's claim to offer the most reliable broadband may not be entirely true.
There are even ways to get more reliable broadband using multiple broadband providers and multiple endpoint hosted FireBricks tunnelling traffic.
I am not sure I can be bothered to hassle the ASA on this, as (a) they won't understand (they even think it is OK to call a copper pair "fibre"), and (b) the advert has already run on TV and the ASA typically just say "don't run that advert again". It is not like they ever make people actually do a retraction of the same scale as the original advert. Imagine that, BT having to do prime time adverts saying "not actually the most reliable broadband, sorry".