I don't remember Cleggie saying that he would go into a pact with the Tories, in the lead up to the 2010 Election either ! But I still can't see him getting into bed with UKIP, for two reasons.
One...The Liberals have nothing in common with a Party like UKIP...none whatsoever. They do, however, have much in common with Labour, as the modern LibDem Party is comprised of old-style Liberals, and disaffected Labour Party member, in the shape of the SDP...Shirley Williams, David Owen, Roy Jenkins, etc etc. If the LibDems could be said to have a "natural" coalition partner, it would appear to be Labour. Indeed, in the aftermath of the 2010 Election, it could have been a LibDem/Labour coalition Government, instead of what we eventually got. Gordon Brown may have been a significant factor in why it never materialised.
Two...For UKIP to be talking about being in a coalition with anybody would depend entirely on how many MPs they end up with on the morning of Friday the 8th of May. At present, they only have two MPs, both hi-jacked from the Tories, and I personally don't think that they will win many more seats this year.
All the Pollsters that I have seen rate their chances of getting more than a tiny few MPs as extremely unlikely. So any talk of a coalition for UKIP is just pie in the sky.
Here are some Polls on the subject of UKIP's chances ::
http://may2015.com/category/seat-calculator/
http://www.electionforecast.co.uk/
http://electionsetc.com/