Battery problem? Car won't start

[slicksps]

So far today I've driven twice, this morning, the starter kicked in and spluttered out. I jumped it from a starter kit and went on my merry way.

On the way back, I picked up a multimetre and checked the battery when I got back, just over 12v (12.34). I checked it a few hours later and it hadn't dropped.

I went to go out this afternoon and checked it just before and it was .01v lower, but when I went to start it, it spluttered out again and had to use the jumper.

On fast idle I get a 13.4v reading so while a little low, I think the alternator is in the clear.

Is there anything else I should test to determine the problem or can I safely assume I need a new battery?

[slicksps]

Ok apparently noone knew so here's what I did for the sake of searchers.

Battery voltage seemed fine, even when under load (High beams) with engine off. Even after false starts, I was still getting an ok 12.5ish volts.

The alternator seemed fine as it was outputting nearly the required 13.5volts.

It starts after being driving but not after being left so the battery was charging but it wasn't holding.

A ran an ammeter through the system when off to check how much power the alarm, radio and clocks were using. A high reading could mean an electrical short. Once the computer had done it's bit, the Amps settled at 14milli amps which is very reasonable considering. - No short, no excessive draw.

Which means that the battery was discharging on it's own... £70 later and everything is running smoothly.