On Profit and Loss report I have entered wages twice in error, as Expense and Journal entry. How do I delete Journal Entry ?

Glad to have you here on the Community, @graeme7.

I can help you delete a journal entry that you had accidentally entered twice. 

To permanently delete a journal entry, you must be certain that it is necessary. Deleting a journal entry can quickly unbalance your accounts.

Note: If you have invited your accountant to review your books, they can also make an adjusting journal entry instead of deleting the original entry.

1. At the upper right corner, click on Settings and then Chart of Accounts.
2. Find the account for which the journal entry was created and select Account History.
3. Locate the journal entry in the account register. The word "Journal" should appear in the Ref No. or Type column.
4. Select the journal entry to expand the view and then click Delete.
5. Choose Yes to confirm.

I'll be sharing this article to help you how to reconcile your accounts, so they always match your bank and credit card statements: Reconcile an account in QuickBooks Online

I'm only a comment away if you have any questions throughout the process of deleting Journal entries. Take care and enjoy your weekend!