I have a Wolseley Swift & have always used A2, they give a nice close clip. I know the A6 & A7 are medium & coarse finish used on some horses but mainly cattle.
Best blades for a Swift are A2 blades, these are the most popular, some people will buy A2F blades but these cut very close. If you have a really thick fluffy or matted coat, a set of A6 blades is handy and should you wish to not cut as close, a set of leg blades will leave 5 to 6 mm of hair, giving the legs more protection.
Whatever blades you use, try and ensure the coat is well groomed and clean before clipping. The blades are well oiled with proper oil, never use WD40 or similar and the tension is correct. Wolseley clippers should clip at quite light tension. I usually suggest, to fit the blades, then wind the nut down until you feel it touch the spring. Then start the clipper and take the blade tension nut down half to one full turn. Listen to the blades, not the motor!, if you wind the nut back and forward you will hear what I mean. As you tighten the blades, you are compressing the concave hollow ground gap between the blades and at the point both blades are just touching, that is correct.Never ever ever, tighten the blades all the way down and then back of one and a half turns. That is correct for a Lister, but will blunt your blades and make your clippers run hot on Wolseley and other makes.