RE: XPS 13 (9343) - Unable to upgrade to Windows 10 - Error 0xC1900101 0x30018
Dell are fixing the problem - if you PM Colin Hurst (who has replied above) with your service tag, he will sort it out. Do not post your service tag in the public forum though.
The problem is caused by the "SK.hynix" SSD specifically, so the problem can be fixed by swapping the SSD for another model. Unfortunately this might mean you lose your installed programs etc - but talk to Colin and see if there's a way around that.
Anyway my issue is fixed now: I have activated Win10 successfully and a new (slightly faster?) SSD! Thanks Colin (and Dell)!