Customer overpayment processing help!

I guess I should have asked this first before attempting to process, but can someone kindly confirm if the steps I have taken are correct?

• 18Nov - issued customer an invoice for £1,500 + VAT (£,1800 total) on a 50% now, 50% later payment basis

• 18Nov - customer pays £900 and I allocated this against the invoice

• 19Jan - customer mistakenly pays £1800 representing a £900 overpayment

• I allocated the £1800 receipt against the invoice to clear the outstanding balance, and the overpayment of £900 to 'Unallocated Receipts'

• 20Jan - I make a bank transfer to return £900 to the customer

Now, I'm left with a £900 unallocated receipt and a £900 debit on my unallocated bank statements

I've tried to follow the guidelines, but I wasn't confident! I have done the following:

• Created an account code called "Overpayments from Customer"
• Assigned this under Current Liabilities
• Assigned as Trade Creditors

Created an invoice for £900, allocated it to account code "Overpayments from Customer" and put this as Exclude from Vat Return // Out of Scope

Reconciled the Unallocated Receipt of £900 to the newly created invoice for £900.

Then, to clear the o/s £900 return payment, I processed this as a Refund, also against "Overpayments from Customer" and again put this as Exclude from Vat Return // Out of Scope.

Did I do this correctly?

Thank you :)