How can we stop Quickbooks taking the feed from our GBP account and posting it in the EUR account page?

The only way to stop the feed is to disconnect your account, Andy24. I'll guide you through it.

Please edit your EUR account in your Chart of Accounts. Then, put a check mark in the Disconnect this account on save check box and click Save and Close.

You can connect your account again and please be sure to select the GBP account in your Chart of Accounts this time.

Feel free to post back when you have other questions about online banking.