Expected profit on Islamic savings products: is that what I'll definitely get?

No. Islamic banks call the return profit, and the figure they announce is usually an expected profit, not a guaranteed interest rate. The actual profit is set on the bank's actual results under the structure it states for the product, such as mudaraba or wakala, and some banks state plainly that their figures are expected and subject to settlement.

Hypothetical example per 100 pounds with an expected profit of 20% a year paid monthly: the expectation is about 1.67 pounds a month. If the actual profit for the period turned out at 19%, it would be about 1.58; at 21%, 1.75. This illustrates the idea; no forecast of where profits will go is implied.

Some banks publish the profits they actually distributed in past periods. Those figures show the gap between expected and actual at that bank in the past, but they are no guarantee for the future.

So any calculation built on the expected profit is an estimate at today's announced rate. Ask the bank how and when the profit is settled, how often it is distributed, and whether it publishes the profits it actually distributed before; and check the key-facts statement for how the profit is computed and the redemption terms.