It's quite obvious toward the end....
Took her home I nearly made it,
Sitting on the sofa with a sister or two.
Oh, lovely Rita meter maid,
Where would I be without you?
Give us a wink and make me think of you.
This is followed by what sounds like masturbation sounds during the coda. And then Paul shouts "I'm leaving!" (opposite of coming)
Well, you asked, so I told ya. 
Never thought of it until now , but yes Lovely Rita could be a masturbation song , it's very lusty and i bet Paul's sofa as seen some action ?
Think Paul might have a thing for uniforms traffic wardens , pretty nurses selling poppies from a tray ,and he did write a song latter called Dress Me Up As A Robber and then there are the Sgt. Pepper uniforms , the kinky little bugger ?
(wink1)
