I posted this originally eighteen months ago, and noticed Pizza Hut are still doing this deal, so thought it was worthy of a repost to remind people.
You can get a Pizza or Pasta or Salad, and garlic bread and a drink for £5.00 per person. (It has gone up by a pound since my last post, bloody recession)
I believe this is instore only. Apparently you will need to ask as they may not have the menus out for this. Its on 3PM to 6PM Monday to Friday.