If England was so satisfied with the current government, then why were the Lib Dems punished so harshly? Was it something like:
Voted Lib Dem in 2010, satisfied with current government -> Conservative
Voted Lib Dem in 2010, dissatisfied with current government -> Labour
Voted Lib Dem in 2010, mostly as an antiestablishment/protest vote -> UKIP
Also, I wonder how much there was polling error, and how much was just a last minute breaking of the undecideds to the Conservatives due to a combination of a) Miliband's personal unpopularity finally catching up to him and b) Fear of SNP influence, and c) UKIP tactical voting.
I feel it is b) and c). Of course b) leads to c).
I notice that there are a lot of Labour held seats in Northern England, particularly in general the more rural ones, where the Tory plus UKIP vote was above 50%, and even more such seats if you put say half the LD vote in the center right column. Several more are very close to that. So that is something that Labour might worry about, if they don't want to become like the US Democrats, and be largely leashed to more urban seats. This might be particularly worrisome for them, if as may well be the case, Scotland, one way or the other, is gone for them forever more.
You can't just assume that UKIP voters prefer the conservatives to labour, any more than you could (as people did) assume that lib dem voters last time would prefer labour to the conservatives. In some areas and seats that's true, but in others its not.
It's not as simple as adding all the "right wing parties" together and comparing with the sum of all the "left wing parties" to find who should win a given seat. To give just reason why, many votes for third parties are protest votes designed to send labour and the tories a message, not an ideological statement.