LETTERS – Can anyone help Janet?

I am a family researcher engaged by Janet Young who was born in Spalding on December 30, 1944. After her birth Janet was adopted by a family named Knowles who were also from the area.
Janet grew up in Spalding and in the 1970s moved to Australia. Although Janet always knew she was adopted, it was only last year that she wanted to establish the identity of her birth parents, so she did a DNA test and was able to access her ‘original’ birth certificate.
After confirming DNA matches and the name of her birth certificate we’ve been able to confirm that Janet’s birth mother was Monica Clark who lived at 24 Matmore Gate, Spalding.
Monica was born in December 1925 and was the daughter of Ethel (nee Speck) and Albert Clark (part of the Clark family who owned the Black Swan).
We also found that in 1948, Monica married Cyril Constable and they moved to Zimbabwe, but that’s where the trail goes completely cold.
We can’t find a death record, I’ve contacted BDM UK and they can’t provide any information and even though Cyril died in Zimbabwe, his death was recorded in a Spalding newspaper, but not Monica (perhaps she’s alive at 99)?
Monica had a brother Stanley Henry Clark who was born in 1930. We think he died in 2006, but there’s no mention of him in any Spalding newspapers, even though I think he lived at 10 Oak Court, Spalding.
So, we have bits of information but need some help finding out if there are living relatives of the Clarks still in Spalding. Does anyone know what happened to Monica, or her brother Stanley (did he have family who would be Janet’s cousins)?
We know that Monica’s father Albert was a bit of a rogue, there are lots of news articles on him, where his own father and brother were preventing him from participating in the family pub/bulb business at Matmore Gate.
Janet has just turned 79, I’d love to be able to give her some info on her birth family.
The other thing is, the name of the father that Monica put on Janet’s birth certificate was Robert Peter Cecil Lewis – however, he can’t have been the father as I found his family and Janet has zero DNA matches with him.
He was with the 3rd paratrooper regiment who were stationed we think in Spalding during the war. So that too is a mystery that we can’t resolve at this point.
If anyone has any information I’d be grateful if they’d email me at amandakmaynard@bigpond.com
Amanda Maynard
Australia