If the timing belt was a problem it would not run, and you had it going before so tell him thats deffinately not it.
As the lads have said, when the battery is dead the starter will not turn and it just clicks really fast but does nothing else. If you got the car started and it would not run when the revs dropped, that points to the battery as well.
No point in putting a new battery in but if its not charging properly, or that one will soon be fucked as well.
Check the battery/altenator by measuring the voltage across the 2 terminals of the battery with a multimeter. It should be about 11.5 to 12.5 volts with everything switched off.
If when you try to start the car the voltage drops way down it points towards a bad battery.
When the car is running, an easy test to see if it is charging is the voltage across the battery should be about 13.5 volts. The altenator could still be a problem even if doing this but so get it checked out at a garage also.