OK... I have a SKY box and have no problem with it as the SKY box switches the format of the TV for me.
Go to the menu of the SKY box and verify that is is on 16/9 and that it is set to send the mode through the scart.
Verify that you have a fully cabled Scart cable, and that it is connected to the TV socket on the back of the sky box, not on the V.Tape socket.
When you go from one channel to another, the BV3 should automatically detect the right format and adapt accordingly.
I am not at home so I cannot tell you exactly which menu you need to go, but if you remond me tonight with a PM then I can check, if you do not find by yourself.
p.