Sorry I was referring more to standard existing property purchase rather than an 'off the plan' purchase that can take years to settle. For example, a standard purchase might have a 40 day settlement period, and is 'subject to finance approval within 20 days'. So then you pay your deposit, have 20 days to get finance approved, if you do then it becomes unconditional after that point, if you dont then you get the deposit back.
For an off the plan purchase where you pay a deposit years in advance, the deposit is held by a solicitor, you can request the solicitor hold the funds in an interest earning account with interest payable to you, but you can't just change your mind and get the deposit back. If you dont want to go through with the deal through no fault of the developer, then they keep the deposit and can also sue you if they can not resell it for as much as they sold it to you for.