Just a quick update for this thread that has saved my sanity. The calibration tool from Sony is a lifesaver, and still works on older Surface Pro 3 devices 1631
BUT when I found it and ran it I got an error message - MSCVP100.dll is missing.
Argh I thought I was scuppered, but microsoft support actually came through - when I googled "MSCVP100.dll is missing. " I was led to download the package below
For 64bit: (URL Removed by Moderator due to direct software link.
Instead, access from here) and that solved my issue!
Ran the tool from Sony again (its already linked and mentioned earlier in this thread) - it did its magic, and my touch screen was restored!!!
Thanks so much to all - I'm also going top stop charging with the keyboard attached
Daisy xx