I wouldn't worry that much, UKIP is polling at a relatively constant rate and is equal to Greens+LD. Currently Labour+LD coalition will give a majority and a Labour +LD+greens certainly does.
And that is just by %, with the FPTP system UKIP will likely get way less seats than that.
Plus the percentages banded about by UKIP supporters are typically an England number. Scotland has much lower UKIP support(4-5%)
Lastly the only thing that really matters is the swing constituencies where there is a tight Labour-conservative battle. It is expected that more ex-tory than ex-labour supporters will switch to UKIP so the more likely outcome is in contention seats the swing will go to labour.