I’ve recently finished my free trial and wanted to go for the basic subscription. When I clicked to do upgrade it made a new account instead of updating my current one?

Thank you for trusting QuickBooks, @alexconnollyheat.

You'll want to make sure that you've resubscribed for your free trial account to get the paid subscription. 

Here's how:

1. Sign in to your QBO account.
2. Go to the Gear icon at the upper right.
3. Choose Account and Settings under Your Company.
4. Go to the Billing & Subscription tab.
5. Select Resubscribe. 
6. Enter the updated billing information.
7. Click Subscribe.

Since you've created a new QBO account, ensure to cancel it so you won't be charged for additional subscription.

Here's how to cancel:

1. Click the Gear icon.
2. Below Your Company, select Account and Settings.
3. Select Billing and Subscription.
4. In the QuickBooks section, select Cancel (paid subscription).
5. Select Continue to Cancel, then Continue to Cancel again.
6. Answer the exit survey questions, then scroll down and select Confirm Cancel.

 For future reference, visit the How to resubscribe or reactivate QuickBooks Online article. It contains detailed instructions and frequently asked questions.

If you have any questions between now and then, don't hesitate to let me know. I'm always here to help.

Thanks but I just want to switch the subscription over to my account I had with the free trial as it has some of my invoices and estimates. Is it possible to do that? 

@alexconnollyheat 

Keep in mind, you will pay the regular price if you pay from your trial account. If you wish to pay the discounted price, you have create a new QBO account by clicking the Buy button.

https://quickbooks.grsm.io/UK

You may consider utilize the trial period of this 3rd party tool to migrate the transactions data between QBO accounts.

https://transactionpro.grsm.io/qbo

Hope it helps.