For Philosophy, write essays on whatever topic you'd like (not necessarily spec stuff; so say if you do animal suffering, you don't have to write about that) using the content. So if you're studying Mill, try to apply him to gender roles, or slavery, or free speech. Make sure you understand the content not just as a school subject, but as something you're genuinely interested in and you can bring up in a conversation you have with your friends. The same goes for Psychology and English Language I would say: try to think about what the effect is of what you're studying, on your day-to-day life and interactions. It will really shed new light on your whole essay-writing process. Biology I don't do or like as an A-Level, so I don't think I can help.
But to directly address the question, you absolutely have time. This Easter vacation will make or break your results: go to the library from 9 to 5 every single working day (maybe take the weekends off) and work solidly. Think about how crappy it will be if you mess up; this will serve as serious fuel when you're feeling unmotivated.
Again, the key here is to not think about it as school work -- think about it as an enriching activity, which, if done properly, it actually is.