hocus focus

Hi, i hope somebody could help. My 1999 1.8 petrol focus will not always start. never had a prob in years but over the xmas period it will not always start. IGN on and turn but no cranking,no dim dash lights,no ticking from starter and no buzz from fuel pump. So looking like immobiliser, LED above clock flash's constantly for a min then im sure once i noticed it flash slowly 5 times,but it has not done it again. Spare key does the same,and i can sit there for hours and it wont go,then it will. Come out next day and it will start,then another day and it wont. When it does start i can go all day start up switch off and she start everytime. One sure fire thing she will do is start if i leave the ignition on for bout 10-15 min. Is this a key code memory loss reset kind of thing or a faulty PCM? I have a new transceiver around the ign barrel.

Thanks guys,hope sombody can help. She got 137k on the clock but is the world to me as everything works A/C H/F/S and all that,dont want to get rid for a silly fault.