I'm glad I'm not the only one with this issue.
It started at roughly the same time as we had a new housemate move in so I was trying to find a way of seeing if he's just completely torrenting stuff 24/7 but the router itself doesn't seem to show particular heavy usage.
I'm in Exeter though - and all the students have just come back to Uni so maybe it is the local network being completely overloaded.
I'm also finding online gaming is suffering - can be fine for a bit, and then suddenly latency shoots up and makes it unplayable.
Luckily I've got an unlimited data tariff on my mobile and that connection works better than the VM one now.