I don't have a No7, but I have found with my No8's and No2MkIV's that they all have different ammo tastes. Sub sonic, definitely, but buy half a dozen boxes of regular .22 ammo and hit the range.
I have had good results with Eley team in one No8, but it's crap in the other one! RWS match is good, SK match, Geco, etc. Winchester T22 works in the No8 that doesn't like the Eley Team, but it's filthy in the bore.

But these .22's are so much fun to shoot that you'll be trying lot's of different ammo just for an excuse to get back to the range!