How can I fix this electrical problem?

I have a Ford Mondeo Mk2 1.8TD Estate 1998. Since we have been having a lot of rain this cars electrics has gon mad. Trying to start the car with new fully charged battery. When I turn the key to 1st position air bag light and coil light come on the dash and start to flicker. Then when I turn the key to 2nd position all the relays start klicking like mad at the same time the windscrean wippers try to work without beeing switched on!! Then if the battery is left in over night it will be drained off any voltage by morning. PLEASE HELP. My cars gon mad!!
Thanks Lynt