Hi Wil,
I followed your advice, and had an email conversation with a really helpful person called Jenny.
I got my username back, which was done by renaming my disconnected profile to something else (to free up the username), then re-assigning it back to my account. However I STILL lost everything, as my history is still tied to my disconnected profile which I can see is still there.
Jenny was very helpful, but ultimately unable to reconnect my profile.
Many members lost their profiles during the upgrade, and its a shame no proper route has been provided to help those affected. There also hasn't been ANY formal acknowledgement or reply to these threads that i've seen. I also replied to the official posts on Twitter about the upgrade (twice), asking for help with our profile issues, but got no response.
Its great the forum has been upgraded, but not so great for those who lost everything as a result 