"Is it just me, or has any other UK 'catters noticed an upsurge in all things "Hallowe'en"?"

Halloween isn't just an American thing. It has been celebrated in Scotland too. The kids still go 'guising' dressed in fancy dress and performing a wee song or joke in exchange for a treat. You do hear the term 'trick or treat' now which you didn't tend to hear much prior to ET but apart from that it is basically much the same as when I was a kid.