Right Now I am very thankful to be able to use the Cambridge University Library, this place has been such a great resource for me. I know that you can get books online but sometimes it is very difficult based on your subject. I am doing a history degree through American Military University, which I am happy to say that quite a bit of people over here are too.
I am able to use this library for free due to my association with the university but I found out that you can also use this place. It costs £10 for sic months but I rest assure you that you will find this as a great resource if you are doing studies as well.
It is huge and a very interesting experience trying to track things down. So far it has been my saving grace.