Premium appointment and health surcharge

[mjtr]

A week ago my wife and I were completing her FLR (M) visa application and went to book a premium appointment. We were ask to enter in the health care surcharge but didnt and decided to wait to book an appointment later.

A week or so later, when filling in the paper application form, we then paid the health surcharge, got the code and added it to the paper form.

We are now trying to book a premium appointment time, and it is forcing me to pay for the health surcharge again. It doesnt give us a place to add our health surcharge code.

Am I doing something stupid? Is there a way of booking a premium appointment and entering in an existing valid health surcharge code? Or do I need to pay it again and claim a refund?

Thanks in advance