william smith was 15 when he fell in love with marilyn buttigieg , then 44 .
met after he was invited round to play computer games with her son .
pair , from crawley , west sussex , say they have proved their critics wrong .
marilyn 's children have all but cut off contact with the loved-up pair .
marilyn , now 54 , left her then husband to be with william , now 25 .