It was only until I had to attach it to the wool (pink) and linen (red), that I realised that the interfacing should have matched up with the wool and linen in some places so that it could be sewn in together - like at the seams. But instead, I stitched the interfacing to the linen to hold it in place, luckily the stitching can't be seen that easily and it's on the inside of the bodice anyway! The wool was then pinned to the back of the linen (right side to right side) and sewn to the linen along the line of the interfacing. After testing it, I trimmed and snipped the seam allowance and turned to the right way round.
To attach the bodice at the shoulders, I had previously left an inch gap when sewing the wool to the linen. I then matched the wool on the front strap to the wool on the back strap, measured 3/4" (I usually have a should seam of anything from 1/2" to 1" depending on how the height of the bodice sits). I pressed the seam flat and tucked it under the linen. I then folded the linen over so the two parts met at the wool seam and then stitched them together.