Found in M&S Simply Food in Milton Keynes Central train station though the staff seemed to reckon the prices changes were nationwide (though obviously depends if the store has any stock left).
Were 25p yesterday and then today the price went down to 11p!!!
There were packs of 4 chocolate lollies, nets of 90g of chocolate ghosts and nets of solid chocolate balls - all were 11p!
I only bought nets of ghosts which are best before January but other things were best before April!
They were going like hot cakes but they had loads, so worth a look if you are near one!