Interim to substantive move

[AbandonGups]

I'm trying to understand my rights and how to approach a situation

In work in NHS. Substantively I'm a B6. I'm acting up to a B7, and have been for 11months.
The B7 post is now vacant substantively, and has been for a little while.
Managers advertised the substantive vacancy recently. I applied (along with others). No one was successful substantively, but my acting up was extended for a further 6 months.
Feedback was that I didn't q "make the grade" at interview (they were more helpful than this in terms of constructive feedback!). I accept my interview was weak in places.
They are advertising the post again.
I've worked on my feedback and getting good feedback in the acting up post.
However, do I need to be interviewed again? I feel like they are using me to cover a gap for their convenience, but yet say that they cannot offer me a substantive post.

Do I have any rights to this post substantively after what will be 18months acting up?
Do I need to be interviewed again?
Thanks.

I don't work in the NHS so I don't know what the policy is on acting up but I would be surprised if it guarantees you the post you're acting up in on a permanent basis just because you've been acting up in it for a certain period of time.

Have you looked at the policy, or at Agenda for Change, to see what they say on the matter?

Assuming you don't automatically have the right to the post on a permanent basis, would you not welcome the opportunity of another interview, to demonstrate how you've addressed their previous concerns?

And wouldn't it be better for them to have you in post permanently because they've chosen that, rather than being forced on them because you've insisted on it by a procedural technicality? That wouldn't start your permanent appointment off on a good footing at all.