<human>: Can you provide a brief overview of the text?

So, I work night shift in a major retail store in the UK.

I used to work 8 hr shifts, from 10pm-6am, 5 days a week. We just got a new manager who has decided to change that to 12 hr shifts, 8pm-8am, 4 days a week. In the UK, it's not legal for night shift workers to be doing longer than 8 hours per night, especially if the job is classed as physical, which mine is. 

I don't know how to approach my manager without sounding as if I'm trying to get away with doing less. It's already affecting my health and I'm unhappy, but I'm worried that it will negatively affect my relationship with my manager. Obviously first impressions are really important, especially this early on in a working relationship. I feel the need to add she is a very critical person and even when you're giving 110% it's never enough. I'm really worried she wouldn't take this seriously even though it's an issue of legal compliance, because I wouldn't know where to take it after this.

I'm not too clear on UK law and I've been trying to find information but it's really difficult. From what I've read I'm sure that it's not legal, but I don't want to go ahead and start suggesting it's not if I'm not right. Does anyone know of any UK law resources they can point me to?
<bot>: I think my manager is breaking the law (UK) in making me do 12 hour shifts on a nights job, total 48 hours a week. 10 hours above what I'm contracted. Don't know how to approach her.