Dataswitcher multicurrency failure

A warm welcome, @CannyCollar.

I appreciate the details you've shared with us. I can see that you've turned on the Multicurrency feature, I'd like to know if you've set the home currency to EUR. This will occur if the Multicurrency is not turned on, or if the Home currency is set to GBP (British Pound Sterling). I'd recommend checking the Multicurrency setup, I'll show you how to do that:

1. Go to the Settings or Gear icon.
2. Select Account and Settings.
3. Go to the Advanced tab and click the Edit or Pencil icon in the Currency section.
4. Verify the Home Currency.

If the Home Currency is GBP (British Pound Sterling), the default accounts will be in GBP. Since you've mentioned that you have EUR and USD customers or suppliers, you can create a clearing account. Create an account for EUR and another one for USD. This is done to move foreign currencies without converting them to your home currency. I've added an article for your reference on how to set up this account: Set up a clearing account.

You may check out this article for your future reference about matching your transactions when your ready: Categorise and match online bank transactions in QuickBooks Online. 

I'll be around if you have follow-up questions about the process. Feel free to tag my name in the comment section. Take care!

Thank you for your reply @MarsStephanieL . I am afraid I still don't understand what you are asking me to do.

Our home currency is set to GBP, as we are a UK company.

I set up a clearing bank account in EUR, as per the instructions, but when it comes to journal the balance I can only make the journal in one currency. GBP.

How do I get the balance from the bank account in GBP to show in EUR so that I can connect it to the Euro bank account?

@MarsStephanieL would it not just be ok to create a new bank account in the correct currency and then transfer the balance using the correct valuation. That way I can link these new accounts to our bank and we can continue in the correct currency.