Test yourself

This website is useful if you want general grammar test practice online:

http://elt.oup.com/student/headway/int/c_stopandcheck?cc=gb&selLanguage=en

A few more free online tests:

Written comprehension:  http://www.englishclub.com/esl-exams/levels-test-wc.htm

Cambridge level test:   http://www.cambridgeesol.org/testyourenglish/

A few mock IELTS tests: http://learnenglish.britishcouncil.org/en/ielts

There are also lots of books available from the Study Centre. I suggest you ask the teacher in there what they can recommend; the stock of books is increasing all the time.

If you know which aspect of grammar you need to revise and practice, you could use:

http://learnenglish.britishcouncil.org/en/grammar-exercises

http://www.perfect-english-grammar.com/index.html

http://www.englishclub.com/learn-english.htm