Wife took unpaid maternity leave in 2011 - Am I entitled to tax back?

Just looking for advice here. My wife was on unpaid maternity leave for approx 4 months in 2011. She is not a higher earner and I already can claim some of her allowances so I pay 20% tax up to the max allowed of 40K.

I'm just wondering, would I be etitled to claim any of her tax credits for the 4 months she was not paid?

We usually don't get our P60s until Feb so am just curious at this stage.

Wouldn't it have been applied to her wages when she returned to work and therefore used?