You should know, all these ISP's use the same BT exchanges. If you are a fair distance from it, you will suffer from an unreliable and slower connection than most others. This is thanks to LLU (or local loop unbundling) which has opened a bandwagon that every company and their dogs are jumping on to. So no matter what ADSL provider you go with, in general you will get the same or similar service. The only difference being the customer support. Also remember this service is running through very old cabling in some areas, and old exchanges.
In short, ADSL is the worst of the 2 types of broadband available. If you want a broadband service AS ADVERTISED, you will need to go with ntl or Telewest (which are now the same company). They use cable/DOCSIS for their broadband services, and you will recieve the full line speed and reliability no matter where you are. Although it does mean uprooting driveways and drilling holes through houses to get it installed if you haven't got a hook up point already.
I have missed ntl and my 10mb connection from the day I moved out of my old flat. ADSL just isnt the same experience in any way shape or form. I have 8mb ADSL with virgin at the moment and hate it. Never get near 8mb - and I'm close to the ancient exchange we have in my town as I live in the town centre.
I do not completely agree. No ADSL service is advertised as 8Mb - those that tried it got slammed by ASA. So nobody is going to expect 8Mb (actually, maximum is around 7Mb).
I wonder whats wrong with your line (or ISP) if you get a poor sync rate (do you get poor sync?) - I am 3.5km line length from my exchange (about 2.5km road length), and sync at 6.3Mb normally. BRAS puts this as max 5.5Mb. Peak time performance isn't great (around 2Mbps download), but faster off peak. Although exchange congestion does exist in some places, its usually the loading on the Centrals that give the problem, and this is down to ISP...
As to quality of BT lines, well, ntl:Telewest ain't much better. An awful lot is still analogue, so knackered before start. Those lucky enough to be on digital can expect some real pain as traffic shaping is coming to cable. Traffic shaping a fast line is far worse than using a stable slower line. Traffic shaping was what effectively killed Plusnet (and made them ripe for takeover - which I believe BT have now/nearly completed).
My gripe is this:
I pay £24.99 per month for an "UP TO 8MBPS" connection with Virgin ADSL.
I used to pay £34.99 per month for a constant true 10Mbps with NTL. Analogue or not, it was a shit load faster.
The latter of which never dropped out, never slowed down during peak times, always got a download speed of 1.15MBps (thats megabytes, not bits). My ADSL connection syncs at around 5-6Mbps, but I rarely see speeds like that unless on P2P networks. And peak times the sync speed drops to about 0.5-1Mbps. I'm seriously not happy with ADSL, and I'm desperate to get my 10Mb download speeds back again. When NTL upgrade to DOCSIS 3, and upgrade the remainder of the lines to digital (my area is all upgraded anyway) then they'll be doing 100mb connections - according to a press release on adslguide (ironically!).
I use my connection for a lot of downloading, and got spoiled by 10meg. I dislike all this waiting malarky i get on ADSL. And I can only play games at off peak times. The latency jumps up to about 200-300ms on peak, which is appauling. I've had quicker 56k dial up (no joke).