I decided to try again, but this time I used very cheap PVA instead of the decent stuff, and was much happier with the results.
Basically, lay the stamp face upwards, and cover with PVA glue - you need enough to cover the image, but not enough to give a thick coat.
I sprinkled brusho powders over the glue as well, and left them to spread.
Once the glue is dry - will take several hours - carefully peel off from the stamp and trim if necessary. Two of my pieces were trimmed down considerably because the edges weren't thick enough to hold together when I peeled the set glue off the stamp -still, they made nice flowers!
A spare piece went onto the cover of a small notebook, with a piece of leftover brusho card as background