discovery 2 v8 auto radio reciever update????

as above i have recently bought a discovery 2000 model 4.0 v8 auto es,once recently when i parked in a different spot outside my house it immobilised itself,it wasnt locked and keys were in house,i did the usual check battery in remote etc anyway after leaving it for ten minutes i tried the remote again and it worked been fine for days now,,anyway was away today and left it at harbour for couple of hours,come back and its immobilised again?? it was not locked and keys were in door pocket,any way hours later and trying every now and then still no joy,so do you think it might be radio frequency interferance with the remote radio unit?? as the harbour has a lot of anntennas etc that could possibly interfere and i think there was problems with early discos,is there an up grade i can get so it wont happen again?? and im going to get eka code tommorow and hopefully move it,any suggestions,ideas would be much appreciated
cheers gus

ok got ek code today free from landrover.was 2 letters and 2 numbers worked it out from posts on here and got it moved,been ****ing down here all night and day,so i had fixed front sun roofs with flashband a while ago, so they wont leak again,anyway water ****ed onto front passenger seat from just above seat belt,so looks like i need to do rear roofs,also took trim off sunroof and can see radio reciever both bolts holding it on are rusty,so hoping its an earth problem with radio reciever,so thats my job list tommorow,will let you know how i get on

make sure the water didnt get to the BCU(behind blovebox) and interior fusebox/IDM(compartment under the steering wheel) cos the fact that the passive immobiliser didnt remobilise it when it was left unlocked is suspect, cos this one has nothing to do with the roof receiver just with the transponder in the key

well its sorted,and it was receiver in roof in front of rear sunroof,its held on with 2 bolts one of them being the earth,it was rusty and water had dripped into the reciever,took it apart and got hair drier onto it for ten minutes clean the earth and bolt also where it touches roof refitted and het presto back to normal!!!!! also fixed sunroof leaks while i was at it
happy disco owner again!!!!!!