Hi @PaulD
Exciting times indeed! 
I should start by saying, I’m not an accountant so I recommend checking anything you’re unsure about that’s accounting related with them
However, in regards to recording the expenses you can create a ‘Fuel’ supplier and logging invoices for them. We have a guide on this here which looks at this in more detail, so I recommend taking a look over this.
But of course, if you need any further help, please don’t hesitate to ask