Cap 413
CAP 413 does state when overflying the initial call should be;
" *Wherever* Radio G-ABCD request traffic information"
To which you should receive the response;
"G-ABCD *Wherever* radio pass your message"
Then you go with who you are, where your going, current position, current altitude, current QNH and where you'll be at what time.
To which they respond with traffic information, runway usage and QNH.
Spru!