Well well, the certificate finally arrived, and I've learnt not to trust everything I'm told...Winifred wasn't a Wiltshire lass at all, but from Wolverhampton...
From this one marriage certificate I've been able to deduce her parents and her mother's parents based on a bit of detective work in the 1901 census (she was living with her uncle in Norwich, which then helped me find her mother's maiden name, i.e. her uncle's name)
I'd still like to find her in the 1911 census though, two years before she gave birth to my grandfather illegitimately...the search for that goes on, but now I'm two generations further back on my Dad's side, so many thanks to all those who helped me in my quest!