Hello, Pamela. I've been looking into this, and it seems like QuickBooks is automatically applying your credit note to an open invoice, which is why it's showing £0.00 instead of £1,000.
To get that PDF looking exactly right, we just need to hit pause on that feature. Let's head to the Gear icon located in the upper right side of your screen, then select Account and Settings. From there, let's find the Automation section in the Advanced tab by scrolling a little bit, and then toggle off the Automatically apply credits feature.
Now, instead of starting from scratch, let's open that £0.00 credit note and check if it's linked to an invoice. If so, unlink it. If that doesn't work, we can go ahead and void it, then recreate a new one. With the automation off, the new credit note will stay unapplied, giving you that perfect £1,000 balance on your PDF.
Let me know how it goes. I'm here if you need any further help.