Well, I was bored at work today and decided to give this a shot despite the radio silence... apologies if this American Folkie makes some mistakes along the way. The tune is, of course, a variation on The Old Gray Mare (Ain't What She Used To Be). There's several good puns in the song (cents-sense and boarding house-2x4)

Transcribed by ear from the YouTube video Joe provided above. Two spots I'm not 100% certain on: "The boss who settled money" and "To get my sanity"

TWELVE PENCE AIN'T A SHILLING
(Tom Glazer)

I was feeling kind of hungry, so I thought I'd buy some bread
Went into the local grocery store
Put down the usual money, but the grocer shook his head
Twelve pence ain't a shilling anymore

CHORUS
And the old pound note don't buy what it used to, don't
Buy what it used to, don't buy what it used to, oh
The old pound note don't buy what it used to
Twelve pence ain't a shilling anymore

Oh, decimals are easy, they only make good sense
The boss who settled money was a bull
That loaf was two shillings, see, now it's twenty pence
And twelve pence ain't a shilling anymore

CHORUS

I was living in a boarding house, my room was rather small
Matter of fact, it was only two by four
The landlord decimalized the rent and moved into the hall
Twelve pence ain't a shilling anymore

CHORUS

Now, my coat was worn and ragged, my shirt began to wilt
Every time I moved my trousers tore
They've been patched so many times now, they'll look like granny's quilt
Twelve pence ain't a shilling anymore

CHORUS

Last Friday I stood in line to get my sanity
Teller laughed until his sides were sore
With taxes and insurance, you've got nothing, minus three
Twelve pence ain't a shilling anymore

CHORUS