Thank you all for your comments.
I didn't have particular settings in mind except I new I wanted a fairly shallow DOF as I wanted the candle bokeh effect in the BG to, as you've all said, give it depth and almost a "magical sparkly" feel and for that reason I decided to shoot in the dark. However to highlight the actual subject I wanted flash. Because I have the yn622 trigger and a transceiver I could use OCF, but at its lowest power of 1/128, which was laying on its side, with a diffuser cap on, by my shoulders, as I was laying on the ground to take the photo. I did try other flash positions but it looked wrong. So for all that, I chose to shoot in fully manual mode with an ISO to suit. I was trying 200 and 400 and I think this is 400 but cannot remember.
I didn't bother trying auto mode to see what the camera wanted to do but I know that's sometimes a good idea to get a basis for the final settings. I doubt it would have been any good in this situation though.
If you look closely, I have tried to clone out the flash reflection on the front of the orange where the red band comes around, I didn't do it very well though as it looks a bit fudged. I should have zoomed in to do it or something as the smallest brush size in darktable wasn't small enough for me to do it well enough. Other than that, I'm fairly happy with the result and I'm glad everyone likes it so far.