This
When infantry sections (IS) are in green cover their damage per second (DPS) is equivalent to always shooting the enemy at point blank range even if they are far away. The opposite is also true. If they aren't in any cover, its like they are always firing at the enemy from max range. Even if they are standing next to them.
Use cover or lose. As already mentioned, Brits in buildings are death. Especially early game. Use your first IS aggressively and see how easy map control becomes.
as a small counterpoint, you can't be all over the map with UKF in the early game like USF or OKW. you need to keep your guys in cover, fight defense in depth, and support your IS with MG or sniper. once you get mid game armor out you can start being a bit more aggressive.
if you treat IS like USF rifles you're going to lose every time.