Currently UK got a hefty boost in production.
I am giving a try against submarines and the like right now being the Allies and indeed shipping is getting pummelled, and hard too.
But it's early 40 and my opponent has also built some extra submarines besides the initial ones.
So time will tell how things pan out.
Right now the RAF has been expanded, Sea Lion not attempted as AA guns were built in all ports to the south, and troops were placed, with ships in positions all with night move not to get bombed, but ready to intercept.
The UK is doing some oversea expeditions as well to help Spain and North Afrika (Vichy), invaded Sirya (Vichy), secured already Iran and Iraq, and seized Crete (whilst Axis is invading Greece).
Ontop of that, Uk is getting ready to secure Azores just in case, for Portugal comes next to Spain.