I’ve just tried to add payroll to my account and basically I’ve ended up with a whole new account ?

Hello there, @steve197.

We can cancel your newly created account so that you'll not be charged on the following month if you've subscribed to a trial account. However, if you've paid the subscription, you'll have to contact our QuickBooks Online Care Team to ask for a refund since you're not going to use it. I'm also going to include the steps on how you can add payroll to your previous company.

Here's how to cancel an account for a trial version. 

1. Go to the Settings icon and choose Accounts and Settings.
2. Select the Billing and Subscription tab, click on the Cancel your trial hyperlink.
3. Confirm by clicking Continue to cancel.

I've also added a screenshot for your additional reference.

If you've paid the other subscription, you can check out this article to speak with our Payroll Care Team: Contact QuickBooks.

After canceling the newly added subscription, you can add payroll to your company by following the steps below:

1. Navigate to the Settings, then select Accounts and Settings.
2. Click Billing and Subscription and select Find out more in the QuickBooks Payroll tile box.
3. Choose the payroll version you wish to add to your subscription.
4. Select Start to confirm the payroll version. Here's how it looks like:
   
   

Once done, you can now set up your business information, for more details please check out this article: Set up and manage payroll schedules.

I've added this article for your future task if you want to track your business' wages in QuickBooks Online: View reports in QuickBooks Online Standard Payroll. This also includes sub-articles about managing your employees and workplace pension reports.

You can always tag my name in the comment section below if you have other questions or concerns. It will be my pleasure to assist you further. Take care and have an awesome day ahead.