Soldato
It's a race. Total time is going to be 4/5 days so 15mins to boil some water for a dehydrated meal doesnt sounds like a lot but when you add in time to stop, dig all the kit out of your bag, setup, cook, eat, clean and pack up again - it can be over an hour of stoppage time. Even if I have just 1 hot meal a day, that'll be at least 4 hours onto my total time.
It's in Scotland so there won't be any huge stretches without resupply. Worst case scenario is about 1.5 days. Although, I'll be cycling for ~18 hours a day so I'd want to eat about 7000 cals in that time.
In my opinion you want at least one hot food meal to look forward to from a morale point of view, especially if you want to be taking in that many calories. A Jetboil is light and can boil 0.5L in less than a minute - you could stop, eat and be on your way in 15 minutes.