help needed

ok so i was driving home last night and i realised thet my rev counter wasnt working so i pulled over and my engine died! the battery was completly flat!

i have a spare battery as i was planning on changing the battery anyway (just hadnt got round to fitting it as the new battery is round terminal and my car is set up for flat)

so i used jump leads to connect the spare and started the car i was looking at the volt gauge and normaly it sits at 12V with the engine off and just under 14V with the engine running. but now it is reading 12V with the new battery running or not and then when i put the lights on the battery voltage started going down and didnt come back up.

so it seems as tho the alternator isnt charging, the other thing is that i have had a few electrical problems recently and was wondering if it could be somthing to do with the fuse box?

the other problems i had where

1) the starter motor became intermitent. that turned out to be the fusebox

2) the fan wasnt cutting in (this was the cause of the head gasket going) still cant find the fault for this yet

3) the brake lights kept blowing fuses. that was a poor connection in the fusebox.

4) my horn has stoped working completly so wired up an alternative

5) the hazzard lights dont work but the indicators do

6) the front fogs dont work but i think that might be the switch as it feels different when you press it (feels like it is broken on the inside)

any help would be greatly apreciated as i cant even get the car to start at the moment as both of my batteries are now flat!!