Mark, good shooting,the Eley Subsonic HP is good stuff, when it becomes available see if you can get some Eley Target and Club to try,cheaper than the Tenex or Match and seems to be more accurate in my older rifles. SK Standard Plus also does well at a moderate price.
5 shot 100yd group from a Winchester 52b using Eley Club.
Try RWS as well. Target Rifle, and possibly R50. Also consider the high-end Lapua.