Your AM only has 120mm? I remember you saying that you were going for the AC with an AM tubeset but that would still be up to 146mm I thought.
Your AM is sounding more interesting by the day.
IF bikes have a few selected retails in the UK and IIRC the ordering process needs to be managed well so it will most likely need to be one of the estabilshed retailers, much like Nicolai. However, unlike Nic, they don't do off the peg frames built to order, they do full custom built to order. I could be wrong about that but if not it means you have to submit a whole lot of measurements before they can build you a frame.