They are all much or a muchness for us mere mortals in terms of energy delivery, with the differences being in flavour, texture and how they sit on your stomach with the extra guff they add to achieve whatever sweetness, acidity, shelf life etc… the manufacturer is trying to achieve.
I can’t stomach SIS stuff as a rule, but High5 works very well for my stomach. Torq is good as well, but I find some flavours a little acidic on my stomach and causes bloating/cramp. At least you can get plain ‘natural’ flavour which is just the base maltodextrin-fructose mix.
The only thing I can suggest is if you didn’t suffer any/many side effects of SIS then stick with it, certainly for Colne Valley as it’s so close and you don’t have much time to experiment. If you think you might want to find something more palatable/less gammy on the stomach, then experiment with trial packs etc.. in training/out on hard/long rides over a period of time. I say hard rides as your stomach behaves differently when stressed compared to just ‘out for a ride’.