I am sure prices will stagnate but I don't expect to see a large crash.
Basic economics, demand exceeds supply, drives prices up. As long as people can get funds in place, demand will stay high. If interest rates were to rise I would expect house prices to stop increasing because a lot less people would be moving/buying based on affordability alone. But I wouldn't expect them to drop significantly as a result, because not that many would be so buggered they would need to sell ASAP.
Best place to be is on the ladder, if you lose, so do people selling the next house you want to buy etc as a general rule. I worry for those who can't afford it and think they can save X by 2017 only to be unable to afford to buy because rises on house prices are faster than those of their savings when the time comes.
I also worry about all those who took out help to buy and if they will manage when rates go up. Great to get on the ladder, assuming you can afford to stay on it.