Maternity Leave & Cover

LegacyUser

Pregnant with my second baby. Had my first 5 years ago. Have been with my current employer for over 12 years. They are not the worst! Like most places I suppose.
After my last maternity leave, they kept on the person who covered me (with no official job to do). Three months after I came back I had to go out sick because the cover and a manager (who the person licked up to) were trying to push me out. They undermined me and interfered in my job to the point it broke me.
I stood my ground and refused to be pushed out. Fine! They managed to pushed another employee out. Which is another story.
So roll on now. I am pregnant along with another employee, and they gave us a maternity handbook which is brand new (the company never had one previous).
The company are taking my previous cover out of their current position and getting them do my job and hiring someone to do their position.
The huge concern I have is in the maternity handbook is states
"You are entitled to return to work to the same job with the same contract of employment. Section 27 of the Act states that, if it is not reasonably practicable for your employer to allow you to return to your job, then they must provide you with suitable alternative work. This new position should not be on terms substantially less favourable than those of your previous job"
This is standard, but I know that but the cover will not willing go back to their old position. Would I better off just to leave or stand my ground knowing I won't get anywhere? The other employee pretty much always gets their own way.
I don't see the point in putting that person into my job then hiring someone in their postion. Its easier to hire someone straight in to cover me as they job is laid out step by step and asier to train someone into.
Just to add this employee has been nothing but trouble since they where brought in to cover me originally. They keep a list of mistakes other employees make. It constantly late and then leaves early. Shouts if they don't get their own way then runs to a manager in a different area to get her way which is ridiculous. When I'm covered on holidays I come back after 1/2 weeks and the person has changed how things are done so its more difficult. Implements procedures for my position without even asking me how things are done. So when we are audited on those procedures it makes it look like I am incompetent and then a big rigmarole begins to prove things aren't done that way all because this person changed the procedure.
Is it worth standing my ground. My two direct line managers are easy to get along with and leave me to work away.