I requested a support callback and spoke to someone. They offered to collect it or I could take it to an Apple store. Chose to take it in in a Tuesday evening. Showed them the problem and they agreed it was an issue and they sent it off. Picked it up 8 days later.
It was in recovery mode when I collected it which meant a 12GB download and took ages (3 hours maybe) but if finally booted and my data was still there. Time Machine might be quicker if you do that.
All fairly easy but took a bit of time.
I requested a support callback and spoke to someone. They offered to collect it or I could take it to an Apple store. Chose to take it in in a Tuesday evening. Showed them the problem and they agreed it was an issue and they sent it off. Picked it up 8 days later.
It was in recovery mode when I collected it which meant a 12GB download and took ages (3 hours maybe) but if finally booted and my data was still there. Time Machine might be quicker if you do that.