Finding a decent English Pub in Paris is sometimes as difficult as finding a working train driver.
Possibly the best, and the certainly the most authentic is the Bombardier. It serves real ale and decent grub and has a happy hour until 9pm. It also benefits from a splendid location right on the place de Pantheon.
This is also where we held a soirée for the language students for the English courses and French courses in Paris that we organise. On the whole it went well though when I tried to introduce them to our 'warm' English beer some of them found it rather peculiar.
It's an acquired taste.