On 16 Jun 2016, at 23:09, Carpii UK wrote:

I'm still trying to get to the bottom of this, but not making much progress

When you get the error please run these tests on your Mac (not via ssh):

# This is what TextMate does and should fail, otherwise the issue is with TextMate
mv file~ file

# This should open ‘file’ in append mode, this might work
echo Test >> file

# This is similar to above but also truncates the file
echo Test > file

# This simply unlinks the file which is what is implicit in first test
rm file

Here I assume that file is the file you want to overwrite and file~ is the temporary file left by TextMate after a failed save.

Please be sure you have a backup of file before doing the tests.

Im starting to wonder if its possible a bundle I use could be

involved somehow?

Highly unlikely.