So I managed to use the Trigo Garmin bike mount I wrote about the other day on my way to work.
I have to say that whilst it performed the job reasonably well, I had a few issues with it.
Firstly, when the Trigo is attached so that it doesn't fold into my wheels when the Brompton folds down, the display isn't in the best location on the handlebars. I can't adjust this without an Allen Key. There is a degree of play, but not enough to get it in a good location for me.
Second, the mount itself wobbles about a bit - the mount itself is secure but it does seem to wobble whilst in it's location. It's not too bad, but it is noticeable. This may be solved by using the plastic washers that came with it, but I didn't fit these as these proved to fiddly to install. I'm not convinced that these would solve the issue however.
In general, it performs as it should but there are a few teething issues. I'll probably look into changing the mount over so it points inwards whilst riding rather than outwards as that'll affect the fold. However, I'll have to be careful with pointing it inwards in case it sticks out whilst folded.
I was planning on replacing the Brompton with a newer one - an M type this time around. That means that I can install the cross bar for some additional room on the cockpit and I should be able to nicely fit the Garmin on with the standard mounts.