Picked up a box of 4 wireless buzzers this lunchtime for the PS3/PS2 £18 in HMV @ The Fort - Birmingham. They had loads left all stacked in various locations around the store.
As usual with instore deals I'm not sure if available nationwide. *update* Looks like it is nationwide as people are reporting finding them in numerous stores.
I'm very happy having been after these for a while. Most places online are selling these £30 plus.