Yet stop I did: in fact I often do. And always end much at a loss like this, Wondering what to look for (19-21)
After saying that a church is nothing worth stopping for, the speaker admits that, no matter what he thinks, the fact is that he does continue stopping to look at churches. The experience always puts him at a loss, though, because he can't quite find the words to say what he's looking for when he goes into a church. In this sense, Larkin does a really great job of working with the lyric model of poetry, since this model traditionally involves a speaker who is trying to express something totally inexpressible. In this case, the speaker wants to express his vague yearning for religion in a concrete way, but is never able to go that far. Perhaps he actually can't go that far, because there are no words that can describe what he's after.
Bored, uninformed, knowing the ghostly silt Dispersed, yet tending to this cross of ground Through suburb scrub because it held unspilt So long and equably what since is found Only in separation—marriage, and birth, And death, and thoughts of these—for which was built This special shell? (46-52)
"Bored" and "uninformed" might describe the speaker of this poem way better than any other words. He's bored because he's not getting the kind of spiritual charge he thinks he should get from the church, and he is "uninformed" because he doesn't have any of the knowledge to know how the interior of the church is supposed to be significant. Uniformed is an especially good word because certain substitutes like "ignorant" or "naïve" don't really do justice to the fact that the speaker is a clever guy. It's just that in this one particular area of life, he doesn't have a lot of knowledge. Now you could go ahead and tell the guy to read the Bible, but there's something that keeps him (and maybe Larkin himself) from taking this step. It could be a lack of respect for religion, or it could be laziness. We don't really know. All we know is that the speaker will keep coming back to churches because he sees some vague value in the fact that churches try to provide answers to life's biggest questions about the meaning of birth, love, and death. Without religion, he implies, we know these things "Only in separation" (50). In other words, without religion we can only know death by losing somebody we care about. We can only know love through heartbreak, and we can only know birth on a biological level. Religion, however, gives all of these things a deep cosmic meaning, which is supposed to help us live fulfilling lives.
For, though I've no idea What this accoutered frowsty barn is worth, It pleases me to stand in silence here (54)
With one line, the speaker devalues the church as nothing more than an "accoutered, frowsty barn," which basically makes it sound as though the church is nothing more than a barn with a few decorations and a false sense of grandeur. Yet in Larkin's classic way, the speaker undercuts this statement with his next line, admitting that, regardless of the building's value, he can't deny the fact that he likes to stand inside the church, especially in silence. There seems to be something hidden and mystical about silence, which serves as a perfect metaphor for the yearning that the speaker can't totally capture in language. For Larkin, this yearning is precisely what spirituality is.
And that much can never be obsolete, Since someone will forever be surprising A hunger in himself to be more serious (59-60)
After wondering about the decline of religion, the speaker admits that religion will never really disappear from the world because people will always feel the spiritual longings that eventually lead to religion and churches. These longings will strike people as a hunger to be more serious and, again, Larkin tries to use words to express a feeling that can never be totally captured in language.
And gravitating with it to this ground, Which, he once heard, was proper to grow wise in, If only that so many dead lie round. (61-63)
After insisting that spirituality will always be a part of human experience, Larkin's speaker closes by suggesting that spirituality is meaningful because there is significance in the fact that so many people over the centuries have believed in religion. There is something to the fact that so many dead people lie around churches and, no matter how much modern skeptics might want to write off faith and spirituality as ridiculous things, they cannot deny the influence that these things have had on the lives of billions of people. In this final line, Larkin might suggest that the thing he finds most attractive about spirituality is the way that it can make you feel like part of a community of other believers that goes back hundreds and thousands of years.