Thank you for expanding on your concerns and compliant @BSK1
It is disappointing that you have not been given the support needed and have had a bad customer experience when switching from the Hub 5 from the Hub 3 and that the engineers were not able to find fault with the Hub 5 itself.
We do offer 3rd party support for instances where the fault lies with a customer equipment rather than ours, this is called Gadget Rescue and is a chargeable service. You can find out more about gadget rescue here if needed.
I'm happy to hear that switching back to the Hub 3 has now resolved the issues you had with your PC and everything is all up and running for you. The follow up that you say has not happened which was promised on the complaint letter, was this a physical follow up by an engineer visit or a phone call, or was this some other promise that you have not seen actioned?