'Hand in glove' is an expression meaning that two things fit togther perfectly, or are very close. OR two people working together, often to do something dishonest.
'the sun shines out of our behinds' phrase actually means 'special or self-important', aka- 'he thinks light beams out where the sun don't shine' or 'the sun shone out of his behind, he could do no wrong.'
OR to love and admire someone so much that you do not think they have any bad qualities.
...or the song could also be about bumming or fisting. If thats how you like to read it. The state of the nation tut tut tut my o my deary me, typical.