David,
I have added a couple of pictures of the assembled frames. You should be able to judge the edge finish, a light filing or polish with wet and dry is all that is needed.
The finished dimentions are very good, far better than what I acheived on my first attempt (abandoned) with a piercing saw etc!
To find a water jet cutter I googled the title and narrowed the search within travelling distance. I then phoned them up to see what the prices were, in some cases sending the DXF file but most seemed just work on an overall size and amterial.
I just picked the one that sounded most friendly with the best price. When I got there it turned out that they specialised in stone cutting for shopping malls but they seemed to have experience in everything and the job only took a couple of days to join the queue.
It cost £11/ plate (I provided the brass) for the cutting so I was well pleased as the time saved was astronomical—at least at my rate of progress!
Hope this helps,
Regards Peter