Hey there John,
Thats what I pay for them round here. AAF's are a quid or so more expensive and thats why I use FX's now.
If you want to be testing for groupings though John, 5 shots of each wont really do unless you clean your barrel between each pellet type and then fire a fair few to reline the barrel with that particular grade of lead.
I would be tempted to say that your scope may not be springer rated if its loosing zero, however:
I would first rezero your scope using the pellets you want to use it with and then fire 30 to 50 pellets and see if it moves again.
Be carefu