Surely service may improve over the coming months?
Absolutely not. BTL's policy is to suppress and block any competition, and as they have a dei facto monopoly (a real one over the infrastructure) that is easy for them. They have shown that they don't mind degrading the service overall if it means they can block one more loophole. So expect the service to get worse, not better.
The way to overcome all this is to install a satellite dish. Not cheap, but bypasses BTL completely. Until they manage to extend their monopoly to include ALL internet usage, as they have already tried to do.
There is an alternative to using BTL's internet service. A competing service is provided by Coral Cable Vision, who also provide all television coverage. But that only competes as far as an electronic bottleneck owned by BTL, and it's after that point that BTL apply all their jiggery-pokery. So The Coral Cable service is just as affected by BTL's blocking policy.
If you need to use a particular VPN, as a number of people working here for major US or Canadian institutions do, make sure that you'll be able to access it. I know three people who had been living and working here who were obliged to leave when BTL cut off access to their VPNs.