15 fuel is only expensive because brits have to tech up early for healing, repair and mine sweeper(situational).
All the other factions can repair and clear mines from their starting unit, brits need tech for this as well. I guess they are tough like that, mine sweeper? Nah brits don't need that
Easy fix that would make the UC more useful in early game strats (low tech strats):
1) replace IS starting unit with a eng squad, adjust manpower accordingly
2) make healing available without tech
That is a very very roundabout way to fix UC, replacing IS with RE as the starter unit is a nerf. We don't need to change the faction just to accommodate the UC, the UC just needs to be changed.
UKF is already playing a tightrope early game as while the IS is good, they aren't exactly USF Riflemen and they have all the weaknesses you mentioned (Need to tech up to heal, no dedicated healer unit)