@white67 : I have just taken delivery of a leased GTE Mk7.5 Advance - and too have a Model 3 reserved 31st March 2016 arriving Q1 2019.
I will share my Man-Maths

on this forum when I have some more time in Oct but I have to admit a bit disappointed with the overall cost / electric savings for GTE. Its currently averaging 15-20miles per full charge E-Mode and my calcs on electricity usage are looking like 4p a mile to run pure electric.
Hence with the slight increased cost (over a GTD which it replaced) and the electric savings I think overall its going to cost me more - although I dont care - I love it!