Being moved roles to cover a mat leave & going to lose weekend enhancement & travel expenses - anything I can do?

I currently work for a community team & I’m being told I have to move to cover maternity leave in an acute post at the hospital because the other staff member & I are employed by the same team at the same grade despite being 2 completely different jobs. I’m not thrilled about it but I don’t think there’s anything I can do. My current post includes weekends & travel expenses but this new post will not. Is there anything I can do to protect my enhancements? I’ll be covering for 13 months and possibly longer.