You are right, that world champion optimised boardman geometry is identical to the tcr. Frames are made by Merida who also have their own bikes - with the same geometry, who'd have guessed?
teen1 had a boardman in medium. I started my racing on that and then i bought a used medium tcr with a 100mm stem as i am 5 10.5". I raced this and went for a medium Defy with a 115 stem because the top tube is 1cm shorter and the head tube angle is half a degree slacker. Hence the extra 15mm. I have a 7cm drop from the saddle and have about 1.25 cm of spacers on the Defy and 2.5 on the tcr.
I upgraded to a Propel as the tcr was damaged in a race. Another medium, but a 110mm stem to match that perfect Defy geometry. That has about 2cm of spacers. All three bikes have the same contact point distances.
For your height, a m/l Defy and a 110 stem should be a good starting point. Shops don't like messing set ups for demos, and stock, the spacers will all be under the stem. Moving out 2cm os spacers will move the bars lower and about 0.5cm further away. So it might feel cramped as is, but adjustment is easy and worthwhile.
I agonised over frame size as i am between the med and med/large for the defy. And i have an ISP, so once cut, it is mine. Medium was the right choice. M/l would be for you. With about 1 cm of spacers, based on your boardman.