So a couple of things.
1, with having 50MB for so long with no issues, why did that suddenly drop by 10MB for no reason. Nothing has changed at all my end. Could be a fault. Carry out the following test which will help diagnose if there is a fault.
2, what was the point of the trip trying to sell infinity plus knowing I'm going to get no increase? They are sales people. It is up to you to check if it is worth "upgrading"
3, how can I test my line distance? As per the following tests
4, do you think that bt 'moved' my line/connection and have our to a New customer to impress them? No
5, if it now drops to 30 what is to stop by stating that my estimated speed is 28 and so all is fine my end? Nothing. The follwing tests will give an estimate of what your line can get.
Can you run this checker and post back a screen shot of the results. Make sure you delete your phone number before posting.
and use this speed tester then scroll down the page and carry out the further diagnostics and post back a screen shot of all the results including your IP profile for up and down. This test must be done with a wired connection.
If you have a Homehub 5 can you post the stats from 1-12 by logging onto the Homehub management pages then troubleshooting > helpdesk. http://bthomehub.home/
If you have the Smart Hub, (Homehub 6) can you go to hub manager then advanced then technical log and post the stats. http://bthomehub.home/
Is there any noise on your phone line? Dial 17070 and select option 2, there should be no noise between the announcements.
Try connecting to the master socket/ test socket and if your problem is still there it could indicate that there is a line fault before the test socket on BT's side.
When you use the test socket make sure that any telephone extensions you have are "dead". There should be no dial tone at any of your phone extensions. If they have a dial tone it means you have star wiring and that is not good for Infinity and will need to be fixed.
According to your stats etc your line is estimated to get between 44Mbps and 64Mbps. Your hub is showing that your line can get a max data rate of 59Mbps and has an data rate of 48Mbps with a noise margin of 8.8.
The noise margin is high it should be around 6 which tends to indicate a line problem.
If you have noise on the line when you carry out the quiet line test you need to report a telephone fault not a broadband fault. Once the fault that is causing the noise on the line is fixed your speeds should start to increase.
Meanwhile try connecting to the master socket test socket and see if your stats improve. If they do it would indicate a problem with eitherthe master socket face plate or your internal wiring.
Yes, noise on the line. Do the quiet line with the test socket first in case the fault is with the face plate or your internal wiring.