national bite the head off a bat day

January 20th, the day the Ozzy Osbourne bit the head off a bat. Why don't you join him in the yearly feast.

Dude, did you know that it's national bite the head off a bat day?

No I didn't, I need to break into the bat roost to prepare the feast.

Ozzy didn't bite that bat for nothing you know!

thrash the head off the bishop

To be engaged in a particularly enthusiastic session of pleasuring one’s self by relaxing in a gentleman’s way

Bollox to this, I’m off to thrash the head off the bishop