just started an extension with imperial bricks and metric blocks, 6 course of imp bricks = 525mm, and weve put the ties in every 6, works out every 7 on the blockwork, so were doing 2 blocks then 1 coursing brick to make it work, i think it will be alright but mate not so sure, building control coming round wednesday for a nose, just don't want to build another load of work and he says its wrong or something, will this be o.k?