In my region banks like Cam/Inter/Valencia etc will normally only go to 70% as a maximum for a foreign person. In some cases in can be 80% on a finished property but this is rare now and Cam have told me that they will be lowering their rate to 70% maximum. This is beacuse they feel they are too much at risk of being left with a repossed property worth less than the mortgage or at least hard to sell in todays market, and the foreign pesron has left the country.
The only time I have heard of a 100% mortgage has been with some very dubious tactics. The broker would get a valuation way over the price from a friendly valuation agent or get a valuation figure of the property price, say in 2 years time when it is finished (this is for off plans)
The banks are aware of these practises and I dont think it could be recommended to go down a route that involves some dubious tactics.
In my opinion if someone can offer 100% the alarm bells should start ringing.