dc42 - Thanks, having looked at this again, I am thinking a 5x5 matrix would be the way to go.
My application is very similar to this:
I'm thinking now I want the days to light up to the current day - So on 14th December, we have 14 LED's lit - But, given a max output of 200ma, thats 10 20ma LED's lit.
Can anyone advise how I might get past this problem? I would need a maximum of 500ma lit (25 20ma LEDs) so 500ma in total.
Please bear in mind I'm new Arduino & Electronics! 