Play the BBC's Word Master game online. There are three levels from easy to difficult. You have a limited amount of time and a limited number of tries to get the correct word. There are a total of ten sentences with a blank in each. You can click for a definition, and you can see how many letters are in the missing word. Even the 'easy' level, however, can be challenging.
The focus of the game is on activating vocabulary. From the context and definition, the player is challenged to come up with the word that fits the blank. It's an excellent entertaining way to practice your British English.
Check out the other games and quizzes on the same page with 'Word Master.' These are also fun and great for practicing vocabulary and thinking in English.