Unsure how to proceed

Question

About a month ago, a neighbour's phone line went dead and bt engineers came to work (for two days) on a box (or something) along the main road. Ever since, our internet speeds dropped from 1.4mbps down (which we got for 3 years, consistently) to 0.7-0.9.
Finally after much much hassle with Orange (who provide our internet), we managed to get a bt engineer down today. He was really friendly and tried a bunch of stuff. He was getting 1 mbps down, and then he went to the exchange and switched us to a different cable. This cable gave us only 0.5mbps down. So after he left, he said he would switch us back. Indeed, an hour later, the internet died a few minutes and he called to say that was done.
However, ever since (hours ago), the speed is still 0.3-0.4 down.
And now when I run a test and go to further diagnostics on the bt wholesale site, it says our max speed is 0.5mbps - when as recently as this morning before the visit, it said 1.0 mbps.
I quickly mentioned to this on the phone and he said it will increase and stabilise again at the 0.9 range after a couple days. When he switched to the other cable it wasn't lower than its max of 0.5, so is it actually the case that it would be significantly lower what we were getting just this morning, but will actually go up? And what about the halving of the bt wholesale max speed listing? Does that mean he did not actually change me back to the original cable that I was on, or will this listing move back up to 1.0 as the line stabilises over the coming day or two? (On the dslchecker page it still says max 1.0.)
I called the engineer to hopefully get us back to 1.4, and now to be stuck on .4 after the engineer visit is pretty frustrating!
Is there anything else I can do at this stage, if not to get back up to 1.4, then to at least get the 0.9 again?
Thanks!

Answer 1

Yes, I understand that, but:
1. It still stands that it was a BT engineer who came today and who effectively halved our speeds.
2. It is the BT wholesale speed test which has suddenly changed its max from 1.0 to 0.5.
I understand that any actual SPEED-related fixes will need to go via Orange. However,  I had questions pertaining why the bt wholesale test site/page would change its max from 1.0 to 0.5, and also if this (as well as the speed) will indeed increase again over the coming days. Both the test, and the transition period of a couple days, are BT products/advice given by a BT engineer. Thus I feel that these questions are perfectly legitimate to ask on a BT forum.
From a BT perspective (not orange perspective) then, I'd like to know:
1. After this cable change (to another one then back), is it normal for the BT exchange to slow my speeds down significantly, and will it generally increase back to normal?
2. Why would the wholesale site show 0.5 max instead of 1? and will this increase again?
Thanks,
Daniel