A few more connection updates.

Time of checking: 04:40
Attainable download rate (kbps): 736
Downstream Rate (kbps): 640
Upstream Rate (kbps): 256
Home phone line: Offline
VOIP line: Online

Time of checking: 05:06
Attainable download rate (kbps): 544
Downstream Rate (kbps): 448
Upstream Rate (kbps): 192
Home phone line: Offline
VOIP line: Online

I called their Home Max number again (0844 873 8586, option 2 then option 5) at 5:10 and was got the "due to unforeseen circumstances we are unable to answer your call" message again..

Time of checking: 05:40
Attainable download rate (kbps): 480
Downstream Rate (kbps): 416
Upstream Rate (kbps): 160
Home phone line: Offline
VOIP line: Online

Still not happy.