What can the government change?

Theoretically, the government can change anything, but it has to have support of a majority in the House of Commons, and the House of Lords for things to be passed. The Monarchy can't actually stop the Government from doing anything- this would cause a constitutional crisis, because the Monarchy is supposed to be above politics, and the people did not vote for the Monarchy. Also the Lords can be bypassed, if they reject a bill three times and it has a majority in the Commons. E.g., the Fox hunting Bill. So, basically anythig, provided that there is enough support for it in the Commons. If the people didn't like it, they would probably rebel, which I suppose might cause the Government to change it back, but this SHOULD never happen, because the Mps are meant to reprisent the views of the people. However, it does all of the time, e.g., student riots over university fees was still passed despite masses of people not supporting it. But I guess that's the laissez faire Tories for you!!