I'm glad you've reached out to the QuickBooks Community. Let me help share some information about the invoice template in QuickBooks Online (QBO) for UK.
Once you display the Shipping option when customizing forms in QBO, this will include the information such as Ship Via, Tracking and Rep No. Right now, there's isn't a way to remove it.
However, you have an option to import custom form styles in DOCX format from Word. From there, you can map the template field. To do this, you can follow the detailed steps in this article: Uploading invoice template to QuickBooks.
Now, if you'd like to add your payment method for your invoices in QBO, here's how:
Customise invoice need to retain Shipping Address but delete Ship Date, Via, Tracking, Rep No but they seem to be tied - also where to put payment methods?
Apologies, I was not specific enough in the second part of my request. However, you seem very knowledgeable so I will try to explain: In customising my invoices I would like to include on the invoice a box containing the methods of payment available to the customer with full details. How can I do this?