Recherche Lionel Welman Jehan

MY grandfather lionel, died in 1952, he was a senior commisioned boatswain at HMS DRYAD near POrtsmouth Hampshire England. UK.He had served bravely in th 2nd World War and had survived being sunk by the German fleet. I believe that his family originated from St Peter Port, Guernsey or the Normandy region of France.He was married to my grandmother, Ena Gertrude nee Cook and they had four children, David, Michael, Fay and Wendy. I know very little about his family at all. I would like to find any information about his brothers, sisters, parents grandparents, and any current descendants I may be related to. Thankyou.