Hi Rowan,
Please find enclosed an example scene. I boosted the glass material IOR so that the reflection problem is more obvious - I use another environment in my "real" scene.
I'd be curious to know if I did something wrong ;)
On a side note, would it be possible to fix the NoTiling bitmap option, so that it doesn't tile in the viewport, please ? it was fixed a few years ago, and now it's back ;(
Thanks.