Yes, usually 10% of the bill. If I bought a meal for 10 pounds, for example cheese burger and chips, I would leave a tip for 1 pound. I would only do this if the waiter or waitress provided me with good service.
Same as us really. We tend to prefer either getting a takeout from our favourite places nearby or just cooking food ourselves. We tend to go and eat out maybe once every 2 months. We tend to always tip because we just haven't come across any bad waiters or staff yet. I'm not sure what the exact amount is though because it tends to be my dad that tips the staff. Whenever I go out with friends, its most places like McDonalds or Nandos so you don't have to tip the staff at places like that.