Honestly? I think it's a bit aggressive and might make them shift it straight over to legal/external lawyers/put them on the defensive. The full/part time thing is just you looking for a reason for the difference at the moment isn't it - not something they've said? If so, I'd leave it out. As you've only just restructured, it could be a genuine oversight, and I think you'll get further if you go gently to start with. You can always roll out the accusations later if needs be.
How about something a bit more like:
"I?m writing to follow up some verbal concerns I raised with you in October about my role and how it compares to that of the OOs in the team. Since I joined the team in October, it has become more clear to me that my role and responsibilities are the same as those of the OOs in the team. However, I am on Grade 4 of the secretarial pay scale and they are on Grade 6 of the management pay scale. This not only means that my salary and holiday entitlement is less, but I also believe it affects my future chances of promotion and progression in my career.
You agreed that we could discuss this in more detail at my review in December, which I would like to do. If there is any information you would like me to gather in advance, or preparation you would like me to do, to facilitate this discussion, please do let me know. If there is any way we can progress this before the review, then obviously that would also be great.
I would also like to address the matter of my fixed term contract. I have worked under a succession of fixed term contracts since I started work at Rosys workplace y 4 years ago. As such, I would like to request that I am moved on to an indefinite contract. Please could we also discuss this at my review?"
[Though, incidentally OP, it doesn't make much difference in law if you are labelled fixed term or perm after such a long time]
What do you think?