Confused

My patter says 315 yds of super bulky wool, how does that translate to British wool thickness and ball weights which come in grams

Welcome to KH!
This is a bit back of the envelope calculation but Super Bulky is about 75-90 yards/100gms. 315 yards is 350-420 gms, depending on the thickness of the Super Bulky.
Usually you can find yards or meters on the ball band and that would be more reliable.
315yds = 288meters.

Thank you, that helps a lot