Mods:
Sleeves and body worked seamlessly. Cast on with alternate cable cast on.
Cables are mirrored, pointing to the front centre.
Button bands worked sideways, 3sts for each 4 rows. 7 rows with buttonholes on 4th row.

If making it again I’d leave neck and sleeve sts live and pick up sts to same qty as full total in collar to 3sts away from front edge before button bands are added. Then work short rows in the ribbing instead of the casting on at the start of the rows that the pattern suggests. After casting off just the short side edge of the collar edging needs sewing in place then.