Why would I need the airfield in sight before I do any of that?
For the simple reason that Approach will not transfer you from his frequency until he is sure that you are going to proceed from your present position to the aerodrome. Last thing anyone wants is a VFR blundering around in the zone following the M1 instead of the M40 or whatever. You can be looking for traffic prior to that point [in fact, I sincerely hope you are!] but the person who knows where it all is in the immediate vicinity of the aerodrome is the Tower bod. Approach will transfer you to Tower once he/she is sure you are going to get there.
...and the correct phrase is "Aerodrome in sight" anyway.
Do I get my "Pedant Badge" now?
DwB