Adverse camber: seen on a road sign for an approaching turn. For example, if you're making a turn to the left but the road slopes to the right on that turn, that turn has an adverse camber.
HTFU: an acronym imploring someone to not be so thin-skinned.
Armitage Shanks: not a word or phrase, per se, but a company. A company, though, that must have a monopoly of sorts, for their ceramic products are in almost every single bathroom I've been in (the UK's "American Standard").
Chin Wag: an informal chat, like in "After the bike ride, I joined my fellow cyclists at the cafe for a chin wag."
Pay at the till: pay at the cash register.
Lovely: a word that is often sprinkled in everyday-type conversations.
Brilliant: see Lovely above.
Mind the gap: anyone who has ever ridden the Underground (London's subway system) has almost certainly heard or read this phrase. It's a gentle warning to passengers, both those boarding and disembarking, to be aware of the vertical and/or horizontal gap between the platform and the train.
Rocket: what us in the States call Arugula.
Knackered: tired, exhausted.
Top up: to replenish something, monetarily. For example, if you have a phone card and it is low on funds, you need to top up.
Single track road: another road sign, letting you know the road ahead is wide enough for just one car going in either direction.
CCTV: closed circuit television. Man! This place is loaded with it, as there are few establishments or streets or whatever that don't have it.
Order at the bar: few pubs have table service, so this is what you do to get your food and drink.