How we cite our quotes:
yet tending to this cross of ground
[…] because it held unspilt
So long and equably what since is found
Only in separation—marriage, and birth,
And death, and thoughts of these (47-51)
Toward the end of the poem, the speaker really starts saying some nice things about religion and spirituality, probably because he needs to make sense of the urge that keeps bringing him back to churches. But on top of that, the speaker feels drawn to religion not just because it gives an outlet to human spiritual yearnings, but because it has done so for such a long time. The speaker can't help but find significance in the fact that religion has been around for so long, because even while he knows that religion is not a permanent thing, it's still been around for an impressive amount of time. By going into a church, the speaker also feels connected to all of the people over the centuries who've found meaning in church, and this gives him a sense of community that modern life doesn't.
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)
Larkin chooses to end the poem with a direct reference to human mortality, mentioning all of the dead people who lie around in churchyards all over the world. But he's not just mentioning them because he has some sort of belief in the power of dead bodies. Rather, he's paying homage to the fact that even though he might not find anything compelling about Christianity, he definitely respects the fact that so many people have over the years. One of the things religion does is connect us to the experience of people who came before us by giving us access to all of the same beliefs that governed those people's lives. Larkin doesn't necessarily share these beliefs, but his speaker definitely seems to have a sense of envy for people who really get to feel this sort of connection across time.