As the spreadsheet linked to in the main post hasn't been updated since October I've done some maths.
This is the state of the LH aircraft as of 1st Jan 2019.
A318 - 0 fitted out of 1 (I know this is a special case)
A380 - 4 out of 12 (33.33%)
B747 - 17 out of 35 (48.57%). I've included CIVF as fitted. It should be returning from CWL any day now. I believe all the 747s that are due to get wifi now have it.
B777-200 - 0 out of 3. Probably won't be getting it due to retirement in 2020.
B777-200ER - 34 out of 43 (79.07%)
B777-300ER - 7 out of 12 (58.30%)
B787-8 - 0 out of 12
B787-9 - 0 out of 18
Total - 62 out of 136 (45.59%)
The remaining 777s that aren't being retired should be done this year, hopefully the 787s will start coming online in 2019 and the A350s due for delivery should(!) be factory fitted.
As for short/medium haul - **shrugs**