I received an reply from Phanteks' customer service team which went as follows:
"Thanks for having interest in our products! The Eclipse P400S Tempered Glass editions will be available in ETA Jan 2017. For more information, please check OCUK for the availability.
Hope to have you informed sufficiently.
Best,
Yun"
I couldn't wait so I went with the "NZXT S340 Elite Tempered Glass edition", and I'm glad that the Phanteks' one wasn't released at the time of my query because the NZXT one looks amazing
.