All they are going to do is trap people on a housing ladder that has a long way to fall still, especially once stimulus is withdrawn and public sector cuts and tax raises make us feel very poor.
Those that have been in 4-6 years would be best advised to stay well clear of government trickery to try and artificially prop up the UK housing market on exceptionally low volumes due to short termist electioneering.
Any wonder the FTSE is down since QE has more or less stopped?