Q: My screen does not rotate

That is the rotation lock & it is not locked.

As I mentioned it works fine if I go into contacts using the home screen.

To explain...

If I get a call & want to save the number with details I click the arrow next to the number on the call log. This takes me into Contacts & it all looks exactly the same as if I was just making a new contact but the rotation does not work now.

Really?

Seems a bit strange to work only some of the time.

I have big hands & find it tricky to use the keyboard in portrait mode (I guess that's part of the reason for a landscape option). If it's a feature to assist why limit it to one access route I wonder?