You don't really need history related work experience, I suppose it would help, but if you don't have any I wouldn't worry. I didn't do any history related work experience and I got six offers from really good unis, so I don't think it's that important. Even if you're applying for Oxbridge I don't think it's that necessary, if you are passionate about history it will come across in your interview and they will be able to tell. If you want to go into a specific career after your degree eg journalism, law etc then i would be better to do work experience in that area.