The version I know and sing (unaccompanied) can be found on a 'Veteran' C.D. WHEN THE MAY IS ALL IN BLOOM by Louise Fuller, but appears to have two lines missing in the last verse.

Tonight I feel so happy, tonight I feel so gay,
Mother's got a roly-poly pudding on the way,
I saw her put the currents in, the suet in as well.
Tonight I'm having 'Spotty-Dick', this story I must tell,
I'm having a bit tonight, I'm having a bit tonight
My mother said I must be quick to get a bit of Spotty-Dick
I like my roly-poly it fills me with delight
I haven't had any since Easter but I'm having a bit tonight
Tra-la-la-la.

Now there is my girl friend, she's such a lovely girl
Her eyes are like the setting sun, her teeth are white as pearl,
There's only one thing wrong with her she isn't very fat,
Tonight she's having Spotty-Dick, so what will she think of that.
Cos she's having a bit tonight, she's having a bit tonight,
Her mother says she must be quick to get a bit of Spotty-Dick,
She likes her roly-Poly it fills her with delight,
She hasn't had any since Easter, but she's having a bit tonight.

Then there's dear old grandpa, he seldom gets enough,
Although he's nearly ninety he's a bugger for his duff
*-----
*-----
So he's having a bit tonight, he's having a bit tonight
His mother says he must be quick to get his bit of Spotty-Dick
He likes his roly-poly it fill him with delight,
Although he's nearly ninety, he's having a bit tonight

                (Still searching for two lines)12.13 GMT