It's great to have you here, @ipp1981.
QuickBooks Self-Employed invoicing feature is currently a simplified version using Pound Sterling (£). The ability to send invoice using other currency is currently not available. What you can do is to create the invoice in Pound and add a note in the invoice to denote the foreign exchange rate for Pound Sterling (£) = Euro €.
On the other hand, I'd recommend keeping an eye on our blog, which is where major QuickBooks updates are first announced: https://quickbooks.intuit.com/uk/blog/.
For additional insights, you may check these articles:
Let me know how if you have other questions. I'm just a few posts away.