What will happen if I stop hrt suddenly?

[Cocolapew]

I have been on it since my hysterectomy a few years ago (no ovaries so on Evorel 50)). At the time I was told to keep taking until I was at least 51, that will be in November.
I'm due to pick up a new prescription for it tomorrow but have been asking around and no pharmacy has it atm. I haven't been to all of them.
Obviously I will start the menopause if I stop taking it but will it be very sudden?
I had very bad symptoms with peri menopause so I'm expecting it to be similar.
Has anyone been in this situation?

I somehow ran out and couldn't get to the chemist so meant I didn't take my HRT for 5 days (previous hysterectomy too)

I felt absolutely dreadful, depressed and miserable.

I managed to get a month supply today so gives me time to see the GP before my next appointment.