Your Sky box should/may still work as a freesat box, and you'd have a channel guide with that.
Your TV may have an integrated Freeview or Freesat tuner (or both, my 10yo Samsung has), so you'd connect the aerial or satellite feed, select the input source and run the auto-tune to pick up the channels. Again both would have a channel guide.
If the above don't work then you can buy a Freesat or Freeview tuner box, which would again need a satellite or aerial feed. I think the newer ones also have an Internet connection and allow you to stream the apps aswell. You'd get the channel guides with these.