As long as your switch to PP completes, assuming you've instigated the switch, you should be OK to stay with PP - of course it will be a long while until the money end is sorted so if you owe Eversmart, or if they owe you it could be months.
It's not clear from your post whether you have actually started the switch to PP. Did you get as far as giving your bank details?
I’m already in the process of switching supplier and it’s not yet complete. Will my switch go through and is my credit balance protected?
You don’t need to worry. If it’s already in progress, you will continue to be moved to the new supplier you have chosen. You should not need to do anything.
When your switch completes and the account with your old supplier is closed, you may be owed money if your account had built up credit with the old supplier. Once the switch is complete your direct debit with your old supplier should be cancelled. However, if this has not happened you may need to cancel the direct debit with your old supplier. We'll look to appoint a supplier who will pay back money owed to you that's outstanding from a closed account.