I'm not sure about changing insulins as I've used neither of those. Could you get advice from your DSN about that?
In general, I always try to keep spare insulin to cover any delay in prescriptions and take my own while I'm away. I don't know about your surgery, but mine lets me add a note to my prescription eg if I needed a double prescription because I would be away when my next one was due.
I know that's no help now, but it may help in future.
Hope you get it sorted!