Here's the version that I sing (fairly similar to the Louise Fuller version - not surprising as I believe she came from a fairly similar area/background to me):

Tonight I feel so happy, tonight I feel so gay
My mother's got a roly-poly pudding on the way
I see her put the suet in, the currants in as well
Tonight I'm having Spotted Dick, this story I must tell

(Chorus: Pretty much as above)

Then there is my girlfriend, she is a lovely girl
Her eyes are like the setting sun, her teeth as white as pearl
There's only one thing wrong with her, she isn't very fat
Tonight she's having spotted dick, so what'll she make of that

The vicar of our country church, he has but one desire
He likes to warm his roly-poly pudding by the fire
He wraps it up in greaseproof, he jumps and shouts with glee
And then he makes a pig of hisself and sings abide with me

Then there is old grandpa, he never gets enough
Though he's nearly ninety, he's a bugger for his duff
He loves his roly-poly, it fills him with delight,
He may be nearly ninety but he's having a bit tonight