"Any advice on the way, ahead"
Never give up, is the advice that I offer.
Just had a prolonged problem with my intermittent speeds and disconnections. Eventually got the ISP(who doesn't want to spend their money) and BT to admit that there was a problem at the exchange. Apparently the problem was hard to detect, except through a constant monitoring process, which I was involved with. Sending reports by a special link.
They should have changed some components at the local exchange yesterday, and I expect a report later today, as to what they have done.
When you do speed-tests, try different ones from different websites as a comparison, including BT's own report speed-tester.
You could also try doing separate 'ping tests', and see what that shows. There are a number of ways for this. Some quick, others more intense. A quick way is to perhaps use click here which will also 'grade' the line being used.
Here's a couple of speed-test websites worth trying click here click here
PC Advisor also have a speed-test facility and link.