I've always had to go back to uni early at easter (and this time I'm not even going home at all) because they always give me loads of work to do over the holidays, plus revision for exams coming soon. I've got all my work stuff set up at uni, it's quieter and I can go to the library or department if I need to. There's only so much stuff I can take home and it's so comfy there I don't do as much work as I should.
They're my actual reasons, but maybe you could use a couple as an excuse?