@adrian-imagestud
Do you need to migrate data from QB Desktop UK version to QB Online UK version? Prepare your new blank QBO account
https://quickbooks.grsm.io/UK
then you may have 3 ways to migrate data:
1. Install the trial version for QB Desktop 2019 to upgrade your file and migrate to QB Online.
2. Contact Support for assistance as mentioned by Ashleigh1
3. Purchase a 3rd party conversion service as the last resort.