Dodgy alternator or starter motor?

[Lewo]

Hi guys, if this isn't allowed on here then please delete mods....

I'm up against time so hence asking on here. The better halfs Punto struggles to start from cold quite a lot, turns over slowly initially. In the winter on the coldest day it wouldn't turn over at all, but that's the only time it hasn't started. I fitted a new battery last summer with 4 year warranty.
On the way to the MOT the other day after the usual struggling start and a 25 mins run it wouldn't start, never done that before. Jump pack got it going and it's started ok since.........
This morning put the meter on battery and it was 12.6V and running was 13.8V.
Do these figures sound ok or is it time for a new alternator or should I test over a longer period than the 20 seconds or so I did to make sure?
Or is the starter motor on the way out....
Cheers if you can help me out 

[Andy]

Could be a faulty battery as well

[oisinc]

Could be several things mate..
Start with the simple things..
Check all conections from alt to battery etc.
Check fuses (Alternator Fuse first)
Check ground wires.

After that get your alt tested and perhaps refurbed if worth it. Possible stuck brushes or bad regulator..

Good Luck Electric issues are a PITA.

[Lewo]

Cheers guys.