Unfortunately, I haven't managed to obtain the behaviour I'm after. I believe that I need to modify the behaviour of the default 'meta.function-call.python' (as indicated by facelessuser), rather than trying to modify my own function lists' regex.
I've tried modifying the first/begin regex in the following - I only want it to capture thisword() but *only *if it's preceded by a dot. But I believe I need to modify the regex for 'dotted.name' as well. But dotted.name has other 'includes', and it's just dawned on me that I probably need to amend all of those as well?! I think that if I could modify the behaviour of these scopes - to only capture single words at a time - then I could just use (.) within my function-lists/scope
It's been a little frustrating especially as the documentation is quite poor. [What's the difference between 'patterns' and 'repository'?]
I've even considered deleting huge chunks of 'Python.tmLanguage'