I haven't tried it myself yet, but your best bet is to maybe purchase a new router + Openreach Modem.
Not the best answer unfortunately, but the fact so many people are complaining and BT are too stubborn to actually acknowledge anything, it's probably gonna be like this for the rest of the year.
The thing is, everyone who posts complaints here are using the Home Hub 5. I've never seen someone post anything negative when using their own private router.
MY experience of BT is the complete opposite. My speed dropped from 19Mbps to 13Mbps....I rang BT ( India ) and an Engineer visit was arranged for 2 days time. BT Engineer arrived at the appointed time.....checked all my Equipment and told me that there was something wrong with the line.......he went away saying he would be back in about an hour......my Wife saw him twice, each time with his head stuck down a BT Culvert.........after about 90 minutes he returned and said that he had traced my Line all the way back to the Box and had made all new connections from my Hub to the Main Cabinet. He then tested the line and hey presto it showed 29Mbps Down and 6Mbps up. RESULT.......that was nearly 6 months ago and my speeds have remained constant with no dropouts at all. I have a Home Hub 5A, I live out in the sticks and the Fibre Cabinet is about 800 yards away. I am on Infinity1.
Try a quite line test
Hope this helps. Any questions I will be glad to try and answer them