I think it's the fibre content that determines whether it can be classed as a HEByou said that he couldn't stop to heat something up, but you can buy those travel kettles and get an adapter to use it through the car lighter, so that might be an option, Comet and places like that should have something.
You can also get cooler bags, and I think heat bags that you can also plug into the same place. It might allow for a bit more variety and something hot on occasion.
The way I see it, if what you are doing works then there is no need to change it! Makes a nice change from sarnies all the timeOh I checked the lot out on the nutritional info box - they were more or less the same. I would imagine if they're not classed as a HEB then it'll probably be because they're flat they don't fill you up as much. I've always counted them as HEB's and it's never affected my loss.