Every UK casino deposit page has a field for a bonus code or promo. The string you type is just a switch; it tells the operator which pre-built offer to attach. The real value is always inside the offer page. So each casino bonus structure, whether it is a Piratepots code or a Zombillion bonus code, follows the same rule: the code opens the door, the conditions decide the game.
Read the full casino bonus terms to see the exact wagering multiplier, game cap and maximum cashout. That includes Piratepots codes, which is a straightforward example of the industry pattern. In the same way, a Zombillion bonus code still depends on the fine print. A no-deposit bonus often looks free, but the same fine-print rules are there.
If you want a real test of whether a bonus can be withdrawn, check the player feed on a UK casino like a rolling slots casino. The number on the code is only the beginning; the actual value appears when the cash-out queue is finished.