Across the board, Fish and Chips is always good, and is certainly the national dish. I haven't had it served to me in Newspaper, but I have had it wrapped in paper.
One fun traditional food that I've enjoyed is the Sunday Afternoon Roast. You will see these everywhere. On Sundays, the pubs will cook and serve Roast Chicken, Beef, Pork, and occasionally Lamb. It is served with all the traditional trimmings: Roasted Potatoes, Yorkshire Pudding, and Vegetables. It is of course the draw to get you in to also have a Pint of excellent, non-refridgerated beer. (Not warm, mind you, just not necessarily cold). I have found that there are certain beers that are served cold such as Fosters. You can also find Bud and Coronas in the bottle and chilled.
A lot of the food is very much "comfort food". The first evening after Tony left to head back to the states, I decided to treat myself to a nice meal, and since it was Sunday, I went out for a nice Roast Dinner at a local pub with outdoor seating. It was covered, and though it started to rain, to was a pleasant way to dine and have a pint for my first night on my own again in London.