These are quite rare. But some property developers offer you a loan for the deposit when you agree to buy one of their new build homes.
For instance, they might lend you a deposit of 20% on the condition that you repay it within 10 years.
This may help you to get better rates on the remaining 80% LTV mortgage. Remember, you have to be able to meet mortgage repayments and the loan repayments at the same time.