No worries guys....I analysed the electrical diagrams last night and it would appear that one (of the 3) supply lines from F25 does feed the Active Security Sounder, or as I would call it, the Alarm sounder unit, which is under the near side front bumper area. I aim to disconnect this, replace the fuse and then see if the fuse still blows. This fault is quite perplexing, since a fault in the alarm unit, which is in a vulnerable area to water etc, seems to result in the loss of all these systems! Driving without demisters, heater blowers, air con, etc etc is not very acceptable I feel. If this is indeed the fault, I am tempted to re-wire the alarm unit to a separate fuse, thus leaving these other systems on their own dedicated fuse. (I managed to write all this without allowing my son to configure my iPad sell chekerz!)