I decided to attach the sleeves to the body by the method Peter shows at Male Pattern Boldness. With the sleeve face up, iron a hem. My seam allowance is 1.5cm so I folded it 6mm. With right sides facing together pin the fold to the raw edge of the armhole. Check that the placket will be at the back of the shirt. My pattern didn't have any notches to match so I just folded the sleeve in half to find the middle and kind of just pinned it around. Starting from the middle I sewed out to the the end of the armhole with a 9mm seam and then did the same with the other half.
Open the folded edge and refold it over the raw edges.
Pin the edge down. (Yes I know I use a lot of pins but with bad eyesight and winter sunlight I'd rather do as little unpicking as possible.)
On the wrong side topstitch close to the loose edge. I sewed from one end to the other. When I come to a thicker part I use this handy bump helper first before the bump and then after it.
First sleeve done.