Thanks janeainsworth - I've finally got around to calling the DWP.
The story is:
a) As I have full NI contributions, my wife's pension would be topped up to that figure.
b) If we don't see a change we need to call the DWP on 08456 060 265, and contact under the 'change of circumstance' category.
c) Also worth noting that the £64-40 figure is for 2012/13, and increases are currently linked to the RPI, which is set at 2.6% as of September this year.
Thanks for your advice - they were as you say very helpful.
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