Here are your answers :)
1. Is there a way of building the site and only having a ‘holding page’ visible to outside world?
Yes, use this plugin http://wordpress.org/extend/plugins/wp-maintenance-mode/
2) 2. PAGES/BLOGS – Typo settings
Make sure you have changed all typography in Canvas/theme settings/Typography and Posts Typography
3. Google analytics:
There is an option with the Yoast Analytics plugin to enter the UA code manually. Try this, it should work – I have seen this message before and doing this has always worked for me.
4) Sidebar – how do I change this according to which page the user is on? ie want to have different Calls to Action depending on what page they are on. Is this all in sidebar manager? is there a tutorial on this?
Use the Sidebar manager to specify specific widget areas for specific pages,
Let me know if that all works!