I've been having the same problem, only noticed it on Friday as that was when I was made Furlough from work, I also have health conditions so I can't go out much, thankfully can get shopping online. Gaming is basically impossible at this point. I pay for 350mbps, and i'm lucky if i've been getting 50 the past few days, it will spike up to 200 max but it will not stay like that, talking to friends they keep saying my voice is lagging and they can't understand me, that's when i'm not even playing any games.
Had an engineer booked to come tomorrow which has now been cancelled after a phone call to say that it is an issue on their end which they're looking into and trying to get fixed asap. Due to 95% of households being stuck at home on lockdown they're all using their internet to their fullest capacity which effects the whole area, at least that's what I have been told. So now I have to wait even longer to be able to actually play anything with no issues. I've been trying to play MW and it's been unplayable pings skyrocket and lag every other second. It's frustrating.