We have same here.
On going to fiber-optic, and sorting other issues, we went from the 10.2 download, 2.6 Upload to the dizzy heights of 17.73d, 3.68u. Super - but short lived!!!
Since then, download has been all over the place, and phoneline clear then constantly crackly. On 16th Oct, as low as 1.19d!
We have yet another engineer re the crackly issue on Monday - let me guess - water in the street collates in the holes where the cable/optic joints are, etc.! blah blah blah
Re the download speed, I'm fully aware that as householders, we constantly get "throttled back" on the service at peak times in areas! OK but 1.19d is farcical! There is a minimum stated on the marketing for their offerings:
Ideal for busy homes that are always online across multiple devices.
Ahem - chance wood bee!
Intend to chase this with engineer and customer support and complaints.
By the way, if you have a company / business line in, Talk Talk are not allowed to throttle back; only for personal accounts!!!
Happy weekend!
p.s. customer support - take note - broadband is used on a Sunday!