If i was to phone sony at there national rate, and they transfer me to there premium number (0844) Will i be charged at premium rate or at national as they transfer me?

For a start they wont do that as they will lose money from the premium rate call, but if they were silly enough to do that then you would get charged the national rate call.

As I said I doubt they would do that they will tell you that you just need to call the number yourself directly.