Underglaze surface decoration: Result
In order to fix layer of applied underglazes I put the dish through a second bisque firing. Then I sprayed it with a clear glaze and fired it to about 1260-1270ºc in oxidation. Somehow the glaze didn't melt properly and it sits as little droplets on the surface. Probably the glaze didn't get hot enough as this dish sat in the bottom of the kiln.
Thus, I have had it refired in oxidation to about 1280ºc, making sure that this time it sat in the top of the kiln. The result is much better. However, I didn't put enough glaze on the dish in particular on the out/underside which is feels a bit rough where it hasn't had enough clear glaze.
The colours have come out darker than expected but I do like the different qualities of decorations and the subtle changes in surface texture. I just need to make sure to pay a bit more attention to the sharp edges of the incised lines.