Many thanks YOKEL! I have been able to rule out both the HINKS and BURRELL marriages, and, unfortunately, lots more besides which has led me to think that Muriel either never married or married under a surname other than Mullenger (and its variants). If Muriel had married, say, between 1930 and 1940, do you know whether she would have had to provide the registrar/vicar with a copy of her birth certificate or another form of identification?
Thank you too, CHEMPAT .. I have waded through the deaths of Alices, Muriels, As, Ms and variants with dates of birth registered as 7/7/13 and drew a blank. I searched a couple of months & years either side of July 1913 too as, from experience, realise that the person registering a death often has no idea of a persons age (even Muriel's aunt, who registered her sister Lottie's death, got her age wrong by 2 years ... and the sister was only 6 years older than Lottie!).
I have searched probate records; burial and cremation records; the London Gazette on line;
www.iAnnounce.co.uk (for deaths, birthday greetings, etc); on line versions of local newspapers for the whole UK in the hope of finding Muriel celebrating her 100th birthday back in July 2013!!
The only thing I am sure about is the fact that my late grandmother really did have a sister called Muriel from whom she had been separated whilst very young - something we had no proof of until earlier this year.
If only we could turn back the clock a few decades ... but that of course would mean we would not yet have access to all this fantastic detailed information at our fingertips!