In English coinage, there are four "sets" of two coins. I don't know if this is the way the English think of their coinage, but it was the only mnemonic I could come up with that helped me find the right coin most of the time. Within each set, the larger coin is worth more than the smaller. The sets are:

• gold-colored - the two pound (actually, gold within silver) and one pound coins.
• polygonal - the 50p and 20p coins.
• silver-colored - the 10p and 5p coins.
• copper-colored - the 2p and 1p coins.

A picture is available at English Coin Set