Quick-and-dirty constituency map (colored according to margin of victory), 'cause what else was I going to do with my Friday night?
It looks like this is what happened:
Tories bled votes to UKIP in the South in seats they had large majorities so not enough to actually lose seats.
Labour bled votes to UKIP in the North in seats they had large majorities so not enough to actually lose seats.
Labour bled votes to the Greens in the South in seats they had large majorities so not enough to actually lose seats.
Labour bled all their votes and seats in Scotland to the SNP.
The Lib Dems collapsed. Votes and seats went roughly 70% to Tories and 30% to Labour in England and Wales and 100% to SNP in Scotland.
The Tories and Labour swapped marginals in equal numbers (Labour won London, Tories elsewhere).
The results was largely a wash from 2010 except the Lib Dems collapsed and the Tories benefited the most, hence their narrow majority. Labour lost seats because they lost more seats to the SNP than they gained from the Lib Dems.
If Boris Johnson becomes the next leader of the conservative party, then assuming the economy doesnt go rotten in five years and they actually hold the referendum and somehow manage to slow immigration. A bulk of those UKIP votes might go to the tories in 2020 which would give them a commanding plurality and another slightly bigger majority.