I'm curious as to the why fuel in the HM or is it just the training runs that you are looking to fuel. (Note: I don't fuel during the HM or shorter. I let the 2-3 days before the race and the light breakfast the morning of be my race fuel source).

I used Gu gels in my last Half/my first Half/oh heck my ONLY Half with no ill effects. That being said, with dubious good effects. I trained with them on training runs over 10 miles. Since I hadn't run over 10 miles without using the GelsI couldn't tell you if they were beneficial. I can tell you, they didn't cause upset.

I also used LyteShow - Electrolyte Concentrate for Rapid Rehydration - mixed into my water which I carried on most long runs and my Half. Had a similar effect as Gatorade/PowerAde without the sweetness or calories. The LyteShow I liked.

The guideline on GUs and other gels usually says take one 15 minutes before the race and one every 45 minutes. I ran my first half thinking I'd need one GU, and that's what I took. 11 halfs later, I've settled into a routine of Sport Beans 15 minutes before (when GUs taste awful) and 2 gels during (about miles 5 and 9, varies a bit based on how I feel). Typical half marathon time is in the 1:30 to 1:34 range.

I found GU Chomps and Sport Beans are too dry and chewy to take during a race, though 15 minutes before is not a problem. I don't get along well with Shot Blox organizationally, though I know other runners who do well with them due to being able to take fewer calories more often. So far, I've used GU gels, Clif Shot gels, and Honey Stinger gels. They taste different, but seem functionally equivalent for my purposes. Litter is easier to control with the Clif Shot get packaging, offset by the fact that they're a little bulkier. Bulkier isn't a significant factor for halfs, but is noticeable for a full marathon where I'll want 7 gels during.

Many other runners use fewer gels than I do. One size does not fit all. I also carry water with me; there is disagreement within the running community on the value of doing so.

I don't typically do much fuel for a HM. I'll carry maybe one Gu with me and just grab water / Gatorade as needed. I will train the same way, so during race, the only thing that is different is that instead of my hydration belt I use when I train, I don't have the added weight. I'll typically down 3-4 GU's during a marathon though, and if it's going to be a super hot race, I'll bring a bottle and nuun hydration or active.

I'm really finding that Tailwind works for me.

I source mine from X-Miles in Dorset, who do a trial pack of different flavours.

I've also found the Gu's. Also agree I can't tell whether it's psychological or not. The best I can say is they didn't hurt in training for my half and running it. During the race I used two; one at 5/6 miles and other at around 10 mile marker.

I use GU and Honey Stinger gels. But I'm not a bold as your folks. Chocolate and vanilla for me.

I have three things I'm doing for running fuel.

First, for races, I make my own gel out of a diluted honey, adding in a bit of molasses. I put it all in a soft flask with a bite valve, which allows me to take a small pull whenever I want, rather than having to consume an entire packaged gel, and struggle to get every drop out while running. This worked great for my only full marathon and I'll use it again next month for my 50k ultra.

Second, I've started making my own energy bars using Dr. Phil Maffetone's recipe as a base. I LOVE these bars!! I bring two bars, which are about 500 calories for the size I make, with me on runs of 18 miles or longer.
https://philmaffetone.com/phils-bars-revisited/

Finally, and most importantly, I'm training my body to burn a higher ratio of fat to glycogen. Keep in mind that I'm training for my first ultra, and plan on continuing with ultras as my main races. For a half this wouldn't be as big of a factor.

I don't bother with anything during runs of 16 miles or less and I've had runs up to 19 miles with no fuel at all (and no water for that matter) with very little drop off in pace towards the end.

I still using packaged gels for long training runs, but only until I use up what I have. Then it will be honey and Phil bars.

A bit late to the party, I know, but since you're from the UK I'll just plug High 5 gels. Apart from the gross banana flavour, I find them smooth and palatable and genuinely juicy (5%-ish real fruit juice). I use the originals, which are not isotonic, so I take them just before a water station. If you need isotonic gels, they're also available but much bulkier for the same carb hit.