Upvote:4
The sign is clearly requiring you to give way, since the alternative is absurd (although literally correct). Note that the double dashed line at the junction also indicates that you must give way.
The sign is not an official UK road sign, and is on private property, not a public road. This sort of mis-signage seems quite common off the public road network: I live near an office park where the sign that should say either "Hey, pedestrians – cross here!" or "Motorists – look out for pedestrians!" (I forget exactly where the sign is) actually indicates that pedestrians are prohibited.
Upvote:6
This give way sign still means for the cars waiting at the junction to give way. The reason for the circular sign is because of it being in a service station where all the signs giving one instruction or direction are circular (I don't know why).