OP it basically doesn't matter if you quit your job, you'll obviously be fine, but consider whether you really need the time off. You should have time to work on your health at the same time as working an entry level job. I can't imagine you're taking work home and busying yourself for all hours with you making £1,500 monthly, so tbh I doubt your job is the reason you're out of shape.
Five months of work at £1,500 a month is £7.5k. That's not nothing, and I'm guessing you're not swimming in money if you're on the max bursary. You could come to regret not having that money lying around.
I say keep the job if you possibly can. You can apply for other jobs while you're there if you want to do something different.