Collectors often ask me why Ancient British coins are generally much scarcer and more difficult to obtain than Greek and Roman coins, and also Gaulish coins. My answer is: far fewer Ancient British coins were minted in much smaller runs over a much shorter timespan.
As you can see, Greek coins were minted for about 600 years, Roman coins for about 800 years and Gaulish coins for about 250 years, whereas Ancient British coins were produced for little more than 150 years. Moreover, unlike Gaul, most of the British Isles was virtually coinless throughout the late iron age (and later). Coin production was confined to south-east Britain – another reason why, overall, Ancient British coins are much rarer than Gaulish coins.