And I found another couple of alternative verses for Freda and Barry, as per a YouTube of Victoria Wood performing her song in 2009:

1st Barry verse:
I can’t do it, I can’t do it,
I’m not exactly Russell Brand,
You’re thwarted – I’m sorted,
I’ve got me evening telly planned,
It’s a pity – the nitty gritty,
I’ve taped 11 episodes of Holby City,
I can’t do it, I can’t do it tonight.

2nd Barry verse:
I can’t do it, I can’t do it, Niagara – Viagra,
Nothing really turns me on,
Not stewin’ – boo-hooin’
I’ve had a good look down there and there’s nothing doing,
Can’t do it, can’t do it tonight.