Thank you Zak_M and staff for sending an engineer to look into this.
After the engineer visit, unfortunately the slow internet is still here with no upload speed.
As the weather is getting warmer in London, the issue is persisting more frequently. If no other Virgin Media customer has this problem in my area, I think it could be a router problem? I currently have Hub 3.0.
See below snapshot of BQM (or see OP for live BQM) of current night's connection. The dip at 11pm is me resetting the router to test if the connection would come back:

I cannot access the internet now, so I am sending this over my mobile data. See below current router logs:
Downstream bonded channels
Channel | Frequency (Hz) | Power (dBmV) | SNR (dB) | Modulation | Channel ID |
1 | 243000000 | 4.5 | 38 | 256 qam | 14 |
2 | 203000000 | 5.1 | 38 | 256 qam | 9 |
3 | 211000000 | 5 | 38 | 256 qam | 10 |
4 | 219000000 | 4.9 | 38 | 256 qam | 11 |
5 | 227000000 | 4.8 | 37 | 256 qam | 12 |
6 | 235000000 | 4.8 | 37 | 256 qam | 13 |
7 | 251000000 | 4.5 | 38 | 256 qam | 15 |
8 | 259000000 | 4.5 | 38 | 256 qam | 16 |
9 | 267000000 | 4.8 | 38 | 256 qam | 17 |
10 | 275000000 | 4.9 | 38 | 256 qam | 18 |
11 | 283000000 | 5 | 38 | 256 qam | 19 |
12 | 291000000 | 5 | 38 | 256 qam | 20 |
13 | 299000000 | 5 | 38 | 256 qam | 21 |
14 | 307000000 | 4.9 | 38 | 256 qam | 22 |
15 | 315000000 | 4.9 | 38 | 256 qam | 23 |
16 | 323000000 | 5 | 38 | 256 qam | 24 |
17 | 331000000 | 5.3 | 40 | 256 qam | 25 |
18 | 339000000 | 5.3 | 40 | 256 qam | 26 |
19 | 347000000 | 5 | 40 | 256 qam | 27 |
20 | 355000000 | 5 | 40 | 256 qam | 28 |
21 | 363000000 | 5 | 40 | 256 qam | 29 |
22 | 371000000 | 4.8 | 40 | 256 qam | 30 |
23 | 379000000 | 4.9 | 38 | 256 qam | 31 |
24 | 387000000 | 4.9 | 40 | 256 qam | 32 |
Channel | Locked Status | RxMER (dB) | Pre RS Errors | Post RS Errors |
1 | Locked | 38.6 | 5 | 0 |
2 | Locked | 38.6 | 4 | 0 |
3 | Locked | 38.6 | 6 | 0 |
4 | Locked | 38.6 | 6 | 0 |
5 | Locked | 37.6 | 4 | 0 |
6 | Locked | 37.6 | 5 | 0 |
7 | Locked | 38.6 | 7 | 0 |
8 | Locked | 38.9 | 5 | 0 |
9 | Locked | 38.6 | 5 | 0 |
10 | Locked | 38.6 | 6 | 0 |
11 | Locked | 38.9 | 5 | 0 |
12 | Locked | 38.9 | 6 | 0 |
13 | Locked | 38.9 | 5 | 0 |
14 | Locked | 38.9 | 5 | 0 |
15 | Locked | 38.9 | 4 | 0 |
16 | Locked | 38.9 | 6 | 0 |
17 | Locked | 40.3 | 5 | 0 |
18 | Locked | 40.3 | 3 | 0 |
19 | Locked | 40.3 | 4 | 0 |
20 | Locked | 40.3 | 5 | 0 |
21 | Locked | 40.3 | 5 | 0 |
22 | Locked | 40.3 | 6 | 0 |
23 | Locked | 38.9 | 6 | 0 |
24 | Locked | 40.9 | 6 | 0 |
Upstream bonded channels
Channel | Frequency (Hz) | Power (dBmV) | Symbol Rate (ksps) | Modulation | Channel ID |
1 | 39399525 | 40.8 | 5120 | 16 qam | 4 |
2 | 46200439 | 41 | 5120 | 16 qam | 3 |
3 | 32599861 | 40.8 | 5120 | 16 qam | 5 |
4 | 25799337 | 40.8 | 5120 | 16 qam | 6 |
Channel | Channel Type | T1 Timeouts | T2 Timeouts | T3 Timeouts | T4 Timeouts |
1 | ATDMA | 0 | 0 | 0 | 0 |
2 | ATDMA | 0 | 0 | 0 | 0 |
3 | ATDMA | 0 | 0 | 0 | 0 |
4 | ATDMA | 0 | 0 | 5 | 0 |
I appreciate if you could look into this again and thank you all for your assistance.