Yeah, I've noticed a few vagaries recently.
Maybe Nominet vary things a bit as a policy, I don't know.
The past week there's been an odd splurge of hundreds of .co.uk's dropping in the 3 or 4 hours before breakfast, and they've been predominantly weird clothing/shoes domains: hundreds and hundreds of them, almost all pretty worthless - I suspect being given up by a registrant from the US, based on a few spellings and terms.
When I'm working I can't track them at all until I get home, but if I have a targeted 'catch' I'll probably be monitoring closely.
I know what you mean though: there's nothing much more frustrating than when you really want a domain, and you wait and wait, and it just won't drop.