Some of the hives I've fed dry sugar to have been throwing it out the front. They do bring it back in after a few days, but the problem is it attracts huge numbers of ants. I also drizzled too much water on it at times to get the bees more interested, but I drizzled on too much water on a few and some of it turned to a syrup and set off robbing. So I've decided the fondant may be best for my girls.
I've been cooking most of the weekend, and must have done 10 or more batches. Since I put into practise the great advice given here, I've had no failures at all. For the first time I feel like I actually know a bit about something related to beekeeping, so am keen to share what I've learned!
To add to the info here, this is what I've been doing and getting excellent results with:
6.25 to 1 ratio of sugar to water, with half a table spoon of vinegar per kilogram of sugar.
This ratio worked best for me - no need to keep heating for long periods of time to lower the water content, but enough time that things didn't happen too fast for me.
I put it on a high heat, and kept stirring. It will suddenly thicken at some point. A minute or so later, I would start checking the temp, and the starting point was usually around 245 or so. As soon as it hit 265 degrees F or so, I'd turn the heat off. Some batches went to 270, but no problems were caused. I found this process quite fast and simple.
I didn't let it cool for long, just a minute or two (I was making small batches though due to cooking pot size constraints!). It was still boiling when I poured it into the moulds. Any large bubbles that rose to the surface I just patted down with a spoon.
I didn't whisk it, I found that dropping samples into water too hit and miss and laborious, and I can run out a batch in half an hour or less. The last batch I hardly had to put my ginger beer down to make! :-D
Regarding sea level factoring, I'm about 15 feet above sea level, so no need for me to worry about that!
Thanks again for all that helped with advice and feedback.
John.