Regarding the law conversion, any degree is acceptable to get onto the course. It's quite common for history and english students to go onto the GDL. It's only cramming in 2 years worth of law (the 7 core modules, as opposed to 7 core and 5 optionals). I don't think many people actually struggle with the GDL since you would have already been through a degree, so just think of it as a masters. If you really enjoy both english and history, but want to go into law, then just do the joint degree as it won't really matter which one you choose.