For those who couldn’t make Bristol’s preeminent ArcTanGent festival this weekend Venture Promotions have put together one hell of a consolation prize. Known as the pre-eminent post and math rock extravaganza, it’s also a mecca that not all fans can make. So that’s why tonight, in the Button Factory, is such a boon. Scooping the proverbial cream from the crop, the saliva inducing line-up includes two celebrated acts from the festival, a UK solo virtuoso and one of our very own. Their name is Yonen and it fell to them to play to the first comers. The group sit somewhere…