Openreach have nothing to do with you. Openreach may have told the ISP that they will provide a "Best Effort Service" what ever that is, but it is irrelevant to you because you don't have a contract with Openreach, your contract is with BT. Do not lose sight of that and do not be fobbed off with "it's Openreach's fault" or any other excuse offered about Openreach.
It may well be down to Openreach to "fix" any problem but as I have said, that is between BT and Openreach and has nothing to do with you.
It is up to the ISP to honour what ever guarantee they have offered. If they can not honour it they have to explain why etc.
Get back onto BT and complain and tell them you want the problem resolved as per their guarantee.
As a consumer you have consumer rights that BT can not ignore.
They have consumer rights, but they do not supercede the laws of physics.
If the speed can't be provided, you'll be free to leave your contract. Nothing more nothing less.
Nobody is disputing the laws of physics and it has already been stated what recourse the OP will have. What is in dispute is how people try to excuse problems by saying it is not BT's problem because it is down to Openreach.
Thanks for the responses all.
I must admit that I'm inclined to push a bit more for an improvement, given the guarantee. Regardless of the laws of physics, I can see the damned cabinet if I lean out of my front door so it can't be that unreasonable. What would I have got if I had signed up for Infinity 2.
Further to this issue. I did another speedtest from the MyBT web pages and, again, it flagged up that the broadband speed could be improved. Following the suggestion to contact BT and subsequent webchat, I have another engineer visit booked for this afternoon.
However, while waiting, I have just used the BT Wholesale speed checker which as given a download speed of 34.64 and a maximum achievable for this line of 35.76. Furthermore it says that if my line is within the range 27.5 -35.76, then the line is working properly.
From this, it would appear that my quest for the guaranteed minimum of 49 Mbps (or something near) is rather pointless.
However, the results from the ADSL checker currently give...
Slightly lower than last time I checked, but still higher than BT Wholesale's line max of 35.76.
Can anyone explain to me why there would be such an apparent difference between the BT ADSL checker and the BT Wholesale tool? Is it just my misinterpretation of the results?
So, the BT Wholesale checker is giving the maximum currently achieveable including any faults that may lie between my router and the cabinet while the DSL checker is giving the maximum achievable assuming no faults at all.