Do You Need Security

Salaam all,

So here's the deal. Do you need a second home to get a mortgage on an new home to buy.

Normally in the UK the bank will:

A) value the property B) take a deposit to secure its interest C) take charge of the property until you pay the mortgage off

I don't have any security or home in Pakistan. But I have a bank account with a good monthly salary - but they say that they need security - Wouldn't a 20 or 30% security be enough?

Tia