I'm trialing the free version of CoffeeCup, and I use SSI in html files.
Works fine on the server (.htaccess lets it).
Question is - I used to have XAMP (Apache etc) installed purely to be able to edit and then test in Firefox locally.

CoffeeCup wont parse the includes to view locally in Firefox - does the paid for version do this, perhaps in Preview (not usuable unless you pay!)

No, it doesn't do it.