I need to do some invoices in euros and some in sterling, is this possible?

Hi there!

For the time being, changing the currency on your invoices is unavailable in QBO. Alternatively, you can utilize the multicurrency feature. 

The Multicurrency feature is available in QuickBooks Online Essentials and Plus versions. You can check your current subscription and if your version doesn't support the feature you might want to consider upgrading. You can click here for more details. 

To learn more about the multicurrency feature you can visit this article: Set up and use multicurrency in QuickBooks Online

Please let me know if you need anything else concerning your QBO account. I want to help in any way I can. Have a good day.