Thanks for that. I have limited experience (one marathon) of Squeezy lemon flavour, which seemed OK although a tad gloopy. I might give SIS a try. On race day last time I planned to neck one every half hour; I think I stopped after a while as my stomach was churning a bit, but came back to them towards the end and they saw me through OK.
I'm not training with isotonic drinks, as I don't plan on carrying a drinks belt in the race - it would spoil the line of my skirt. The only thing that's gonna taste good at 15 miles is one those high-carb malt drinks that come in pints. Best save that for the finish methinks.