Freecall or not

[torob]

Hello,

I'm confused when to freecall and when not.

Flew from Biggin Hill to somewhere on the mainland. Because it was VFR I had to remain outside controlled airspace in the UK.
After Biggin I had to contact Farnborough radar, requested basic service and passed my whole message as in my opinion controllers don't have to coordinate with the next controller in uncontrolled airspace and therefore won't be aware of your flight. After Farnborough I had to contact Manston radar where I gave again the whole message.
Mid channel Manston instructed to contact Ostend Approach. I thought that because I was in uncontrolled airspace going to controlled I had also to freecall again on first contact but after calling "Ostend App, XX-ABC" they replied with "XX-ABC, radar contact" so apparently Manston coordinated this with Ostend. Because i was not really prepared to get this reply I eventually passed my whole message again which was of course not nessacary.

I know when you are going from one controlled airspace to another you just pass your heading or 'inbound to' and your FL or alt but can someone explain what you can expect in the other circumstances? What if you are going from LARS or FIS to another (controlled) unit or in the opposite direction?
I searched already in the CAP 774 and 413 but couldn't find anything related to this question unfortunately.

Thanks in advance