At the moment there is a chance of this due to the market slump. People & Developers are selling properties well under market value / bank valuations. If you manage to get a very good deal on the property ie its worth 100k and you get a 30k discount and you pay 70k for the property, you are able to get a 70% mortgage from the bank but in terms of the finances it works out to be 100% of the mortgage.
The other way this can be done is get an over valuation done by a commercial surveyor or someone similar. Ie you are really paying 100k but its been over valued by 50k etc so instaed of getting 70% of 100k you are now getting 70% of 150k which is obviosuly more.
There are various ways of doing it, but its not straight forward.