I have been on Sky for over a year (unlimited package from memory. No limits but not fibre), but the past few weeks have been a bit unbearable during the day. The connection is up but so, so, slow at times.
Switching providers is of course an option but I am a little concerned that it might not fix anything. If it is due to contention, if switching providers likely to make a big difference (or is the equipment where the contention occurs shared)? Another option is to switch to fibre, but I don't want to be stuck on fibre for 12 months and have the same problem too..