Had csf leak repair last year is a c section recommended I’m due 2nd October. I’m worried about straining if have vaginal birth?

Wouldn't worry. The common blood patch done after a Spinal/csf leak is temporary and disappears when your body repairs the hole responsible for the leak. The tissue is now as strong as it ever was. If it were prone to opening it would have after you took a hard poop. Your type of delivery should be a balance between your personal desires & the issues that arise in labor.