Security deposits are normally returned within 10 working days.
If it has taken longer than this, please check with your bank that the money has actually been taken as UCPA do not actually taken this money from your account (as it is a pre-authorisation), it may appear on your statement, but please confirm with your bank whether the money has been taken.
If using a Monzo or Revolut, it seems a common fault of the app to not properly release the preauthorised payments back into your accounts. In our experience they appear much later than usual.
However, after checking with your bank please let us know and we can then investigate further as to why you have not received it back yet.