Robin,

Actually, I thought about this in bed last night, and grinned when I realised the answer. CNC! All I need to make holes in the solder mask is a CNC drill. I'm fairly sure the CAD outputs a Gerber file that will either do the job as it stands, or will do so if I just fiddle a bit with the hole sizes. But thanks for the link to that mask manufacturer. I've made a note of them, just in case. The price is certainly right. As a general rule I like to keep as much as possible in-house, for both cost and quality reasons. But sometimes it can make sense to contract out.

And yes, it's true that I don't really have to use a robot arm. I could just as well do it by 2D XY positioning. But that's just a tad boring, and I have to have a challenge in it somewhere to keep up my interest. Besides, a robot arm will impress the hell out of the customers; and although it's irrational, in real life that's an important part of getting contracts. :) Then I can make vids like the one Tom posted!

Ian