Thanks for all the replies, however, it turns out that the in built tool and promise of 'seamless migration' is a bit of a tall story. The tool doesn't work, and most of the online help in regards to 'how to migrate' are false.
after chatting with QuickBooks support (UK) it transpires that you do have to use a third-party tool provided by Movemybooks. This would usually be a chargeable service, but in this instance (as the QuickBooks tool doesn't work), then QuickBooks pick up the bill.
See below link.
https://quickbooks.intuit.com/learn-support/en-uk/help-article/accounting-bookkeeping/move-quickbook...
From an experience point of view, then the migration went relatively well other than not all of our products and services migrated successfully. This was due to our products and services being set up as higher level and sub products. Something which the desktop version supports. However, the online version has no support for subproducts and as such ignored all the subproducts, so watch out for this issue when you migrate!
Dave
