Totally agree with Sasha13 & Buenchico.
It's really optimistic to expect the 100% mortgage until house prices are really on the up. Considering that lenders that went this way are the ones in the most trouble (HBoS, Bradford & Bingley) it will take a HUGE amount of risk and confidence in the market to predict it will rear its head again any time this decade.
As for a mortgage with less than a 25% deposit, I'm not sure that it's a good idea either.
Have a look on the BBC's website here -->
http://news.bbc.co.uk/1/hi/business/7807724.st m . It doesn't bode well for house price increases any time soon. I'd say keep on saving, keep on watching.