Something has changed.
After years of getting TBB speed test results way below my actual speed I am suddenly getting results near my paid-for speed.
Does this mean that the TBB connection to my part of the VM network has been improved after so long, or has the quality of my own connection suddenly improved?

That doesn't really make sense; VM can't make your connection to a specific site any better, unless they
really really wanted to, and were willing to spend lots of money. As a second point, an improvement to your local network consisting of "whatever" will of course make your connection better if it's done correctly; but that, by definition, won't be done just for you.
Your connection has got better - yay, etc.
If you want to make it even better then follow the generic steps from guidelines on here, nothing you've mentioned makes your connection's circumstances unique.
Edited by deleted (Wed 22-Nov-17 11:17:32)