Good effort...
...but completely pointless.
I get a good 5 months or so out of 2 AA batteries [sic] in my wireless 'board, pretty much only 4 a year. When it comes to saving the planet I think there are possibly better ways to expend brain power. And £65? It would take 20 odd years to offset the cost of batteries+regular wireless keyboard. The chance of a coffee related accident in that time must be very high reducing the average keyboard's lifespan considerably.