Common names are deceiving Gary. Englishmen travelled the world and saw something that reminded them of home so called the bird that. Robins is a good example, "It's got a red breast, must be a robin readbreast", there are different birds all over the world all called 'Robin', our original one is an insectivore which is highly territorial, living solitary, or as a pair sometimes of year, and fights to the death if another one comes on its territory. The American one is a type of thrush that flocks and migrates, couldn't be more different. I didn't know about your wren, but ours is super shy, builds a little domed nest right in the middle of dense bushes. In winter they sometimes gather in large numbers to keep warm in places like hollow logs. Hedging and ditching was a winter job and people who never saw a wren's nest would disturb them, and thought they grew out of the ground, hence their Latin name. Troglodytes troglodytes.
You are perfectly right about attracting the right ones though, for example, great tits are fairly common here, and feed their young caterpillars, but they time their egg laying and hatching to the emergence of oak tree caterpillars and feed them exclusively. No one knows how they manage the timing, the caterpillars emerge with the new leaves and it is different every year, but the eggs have to be laid well in advance. Birds are amazing.
These boxes have a fairly large hole compared to the ones I already have, so I am expecting sparrows rather than bluetits, and they seem to be untreated, so I'll take them down and give them a coat of something late summer, and build some different sorts, but they are a quick, easy way to get started now when the birds are just looking to start building.