Cameron has run a frightful campaign, even trying to curry-favour with the working class, attending BBQs, but eating with knife and fork. The UKIP and the Euro-sceptics are peeling away support and there is no hope in Scotland and Wales.
Milliband, of Labour, lacks fire and gravitas. The Scottish Nationals will strip away the votes that could have given him a majority but bitterness in Scotland over the referendum defeat means that voters are turning to the National Party, which may end up holding the balance of power and pushing its left-of center policies.
The Conservatives should have benefitted from the economy, but Cameron has not been seen as a strong leader, especially on the issue of Europe and Britain's continued membership. Labour which mounted a very strong campaign against Scottish independence ( with Brown doing yeoman's service), will lose most of the 44 seats it had in the last Parliament and the Liberal Democrats,. will be caught in the middle, in the fight between Labour and Conservative.
Britain has been moving away from the two-party system to a two major, three minor party system. It means more equitable representation but weaker governments, whether minority or coalition.