Ballet pumps too small!

[Lollypolly]

Bought some lovely ballet pumps in Zara the other day in my usual size and they felt fine in the shop. After wearing them a couple of times, they are giving me huge blisters on my heels and feel tight - any suggestions for stretching them?

I've heard you can get them professionally stretched at a cobblers.
I had to get a bigger size in Zara ballet pumps for the same reason - they are tiny.

Yes, I've had several pairs of shoes, including ballerina type ones, successfully stretched by my local shoemender.