The ubiquitous challenger to the 'Keep Calm and Carry On' is 21. Interesting read via It's Nice That: A testament to a printed, physical thing”: Anthony Burrill’s Work Hard and Be Nice to People turns 21
If you're interested in purchasing any of Burrill's work, I'd recommend Nelly Duff in East London for a curated selection or some of the classics are available as open editions via Antony Burrill's own shop.