Invoice with dual currencies

We have set up an option in the shop where customers can pay on account. This works fine in the UK as customer creates order, and then the client prints out the invoice and sends with the order for the customer to settle.

But when a customer from a european country does this we really need his invoice to be in euros, is this possible?

Which of your partners are suited to a small job like this? I would the prefer to use a PHP developer who knows Hikashop really well