Thank you most kindly Dave!
Many thanks indeed Dave, I certainly appreciate the positive comment!
Thank you Mark, very kind of you to say!
It was a pretty straightforward setup really.
Here is a pic I quickly put together....
The green gel flash was below the level of the tile and pointing upwards, fairly close to the diffuser.
I tried placing it behind the diffuser at first, but couldn't seem to get a nice gradient, so I went in front and took a chance that no splashes would fall onto it!
Once this was dialled in, it was just a matter of fiddling with the flash settings to get the right balance....and of course chucking many cupfuls of water at the bottle!
It took about 30 or so throws to get a good result.