Slow speeds all day / week

I have been receiving very very slow speeds all day, and most of the back end of the week, since Wednesday. I'm unable to load web pages let alone stream video or use online gaming.

When doing various speed tests I have got speeds as low as 0.02 Mb/s.

Any info on why this is happening? Weather? Flooding? Exchange?

We have recently switched to TT but were told the connection would stabilise after a week, and it's now been 3 and during the second week speeds had been fine and consistent at around 20-27 Mb/s.

Tried restarting the router various times and leaving it off for a good 10 mins or so.

Any help would be nice

Thanks