fix one thing and along comes another!

I ve now got brake lights and hazard lights!!   

Now the car wont start!
The battery is dead, but it cant be its brand new, I get 12v at the battery with the volt meter and the car jump starts fine. All lights etc still work but the battery will barely turn it over!!
Any ideas??
I ve just fitted another set of clocks with a rev counter, is there a possible link there do you think?
Thanks
Sam
P.S. the rev counter doesn t work!! But the rest of the clocks do.

Update:
Put the old clocks back in, still the same.
I ve now charged up the battery, reconnected it. Gonna leave it over night, if it starts tomorrow night i think i ll be inclined towards a dodgy alternator. If it doesn t start, i have a battery drain to find  

hey wilco, how would u go about finding a battery drain??? Its something i might need to do tommorow as my battery aint holding its charge over night.
Cheers
Charlie