PLEASE help me find this book...

OK, I knew there was a reason for starting this blog - I now need the help of all my readers... YES, THAT'S YOU!!!
I bought a book many years ago (well, about 1993/4) and read it over and over and over again. It was falling to bits but lovingly sellotaped back together again until one day, it was lost forever during a house move :-(
I can even envisage the cover... it was a drawing (not a photo) of the back view of a woman in a fitted red dress, turning slightly as though she was viewing herself in the mirror.
I bought it in a book club 3-for-2 deal and the other two books were "Hungry Women" by Laramie Dunaway and the other was "Wicked Women" by the same author, both published by Warner (I think). It will have been written/published around 1990-1991 possibly.
Here is the story line:
A lady needs a break from "real life" and goes off wandering in town. She walks down a side street that she's not noticed before and stumbles upon a dress shop. She goes into the dress shop and wanders round the rails. Each rail is dresses from a different era; 80's, 70's, 60's, etc. She tries on a couple of dresses but the shopkeeper encourages her to try something on a bit older. She offers her a red, floor length dress that is from the 1920's but looks brand new (it's a bit like Mr Benn at this stage). 
As she's trying on the dress she feels a bit dizzy but admits that it fits like a glove, and looks fantastic. She pays for it and goes home. 
In the evening, she tries the dress on again and feels dizzy again and faints. When she comes too she's travelled back in time to the era of the dress but everyone thinks she's another woman. When she checks out pictures of this other woman, she realises that they indeed do look very similar. She carries on the life of this other woman. 
In the meantime - the other woman is now in the 1990's and is trying to come to terms with HER new life (modern, fast living) with only the knowledge of the 1920's.
Anyway - it's about how they cope with what's thrown at them, how they seem more suited to the era that they've travelled to and how they make contact with each other.

PLEASE help me to find the book as I am convinced I imagined it!!!!