Conventional wisdom has it that UKIP are to the "right" of the Tories, and thus voters abandoning UKIP would instead vote Tory.
I've always been pretty dubious about this, and thought that UKIP was just as likely to attract Labour voters. After all, their main two policies (anti EU and anti immigration) have support across the political spectrum, and their other policies are just as likely to be "Old Labour" as anything.
UKIP thus illustrates the limitations of a simplistic left-right spectrum analysis. UKIP tend to get called "hard right" mainly because a lot of mainstream commenters dislike them, and such people tend to call anything they dislike "hard right".
Anyhow, have a look at the chart of polls here:
http://metro.co.uk/2017/05/30/latest-polls-show-labour-narrowing-the-gap-to...
What is striking is that the recent collapse of UKIP support is coinciding with a large increase in Labour support. Coincidence? Maybe not. Maybe a lot of UKIP voters always were typical Labour voters, and they are now returning to Labour? The upswing in Labour support has to be coming from somewhere, and maybe a lot of it is from UKIP?