The wrist bands are no allowed here so, I wear my wristband out of work & bought a H4H watch strap via the H4H website for my work watch.
I can see the argument against them being worn. If you allow H4H wristbands then by default, you are allowing ALL wristbands as the Service cannot be seen to be biased towards a particular charity.
That said, we are encouraged to buy a poppy every year from another registered charity...