first registration - permission to remain but no registration appointment

[GeekyPete]

We have an EUTR1 application submitted for my wife, got email confirmation and have sent the documents by mail as requested. They have replied she has the right to remain in the state but only have that in an email and no letter back yet confirming this.

With the holidays coming up and just a few weeks left on her 90 day stay getting quite worried seeing how difficult/impossible it seems to be to get appointments at Burgh Quay.

If we get the letter in time confirming her right to stay is that enough or will she be overstaying if she doesn't manage to get her appointment for registration and first stamp in time within the 90 days?

[GeekyPete]

We just got the confirmation letter today asking to get an appointment at Burgh Quay to get a stamp 4 - no clear answer what happens if we are unable to secure an appointment in time.

Is there a process to try and request an emergency first time registration appointment?